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Insulin resistance is a feature of pregnancy and is associated with increased levels of angiotensin II (Ang II) and insulin. Therefore, pregnancy may change insulin-induced vasodilation through changes in Ang II receptors. Insulin-induced vasorelaxation was evaluated in phenylephrine-precontracted aortic rings of pregnant and non-pregnant rats, using a conventional isolated organ preparation. Experiments were performed in thoracic or abdominal aorta rings with or without endothelium in the presence and absence of [N.sup.G]-nitro-L- arginine methyl ester (L-NAME) ([10.sup.-5] M), losartan ([10.sup.-7] M), or PD123319 ([10.sup.-7] M). ATI and AT2 receptor expressions were detected by immunohistochemistry. Insulin-induced vasodilation was endothelium- and nitric oxidedependent and decreased in the thoracic aorta but increased in the abdominal segment of pregnant rats. The insulin's vasorelaxant effect was increased by losartan mainly on the thoracic aorta. PD123319 decreased insulin-induced vasorelaxation mainly in the pregnant rat abdominal aorta. AT1 receptor expression was decreased while AT2 receptor expression was increased by pregnancy. In conclusion, pregnancy changes insulin-induced vasorelaxation. Moreover, insulin vasodilation is tonically inhibited by AT1 receptors, while AT2 receptors appear to have an insulin-sensitizing effect. The role of pregnancy and Ang II receptors differ depending on the aorta segment. These results shed light on the role of pregnancy and Ang II receptors on the regulation of insulin-mediated vasodilation. Key words: pregnancy, insulin, angiotensin II, AT1 receptor, AT2 receptors, aorta. La resistance a l'insuline est une caracteristique de la grossesse, elle est associee avec une augmentation des taux d'angiotensine II (Ang II) et d'insuline. Par consequent, la grossesse pourrait entrainer des modifications dans la vasodilatation provoquee par l'insuline par l'intermediaire de variations au niveau des recepteurs de l'Ang II. A l'aide d'une preparation d'organes isoles classique, nous avons evalue la vasorelaxation provoquee par l'insuline dans des anneaux aortiques precontractes par la phenylephrine chez des rates gravides ou non gravides. Nous avons procede aux experiences avec des anneaux d'aorte thoracique ou abdominale avec ou sans endothelium et en presence ou en absence de L-NAME ([10.sup.-5] M), de losartan ([10.sup.-7] M) ou de PD123319 ([10.sup.- 7] M). Nous avons detecte l'expression des recepteurs AT1 et AT2 a l'aide de l'immunohistochimie. La vasodilatation provoquee par l'insuline dependait de l'endothelium et du NO avec une diminution dans l'aorte thoracique, mais une augmentation dans le segment abdominal des rates gravides. Le losartan entrainait une augmentation de l'effet vasorelaxant de l'insuline, principalement sur l'aorte thoracique. Le PD123319 entrainait une diminution de la relaxation provoquee par l'insuline, principalement dans l'aorte abdominale de rates gravides. La gestation entrainait une diminution de l'expression des recepteurs AT1, mais une diminution de l'expression des recepteurs AT2. En conclusion, la gestation entraine des modifications dans la relaxation provoquee par l'insuline. En outre, les recepteurs AT1 entrainaient une inhibition tonique de la vasodilatation provoquee par l'insuline, tandis que les recepteurs AT2 semblent avoir un effet de sensibilisation a l'insuline. Le role de la gestation et des recepteurs de l'Ang II varie selon le segment aortique. Ces resultats mettent en lumiere le role de la grossesse et des recepteurs de l'Ang II dans la regulation de la vasodilatation mediee par l'insuline. [Traduit par la Redaction] Mots-cles: grossesse, insuline, recepteurs AT1 et AT2 de l'angiotensine II, aorte., 1. Introduction In addition to its metabolic role, stimulation of the insulin receptor (IR) plays an important role in the regulation of vascular tone (Manrique et al. 2014). Insulin binding [...]

An essential link between the kidney and blood pressure control has long been known. Here, we review evidence supporting the premise that an impaired capacity of the kidney to excrete sodium in response to elevated blood pressure is a major contributor to hypertension, irrespective of the initiating cause. In this regard, recent work suggests that novel pathways controlling key sodium transporters in kidney epithelia have a critical impact on hypertension pathogenesis, supporting a model in which impaired renal sodium excretion is a final common pathway through which vascular, neural, and inflammatory responses raise blood pressure. We also address recent findings calling into question long-standing notions regarding the relationship between sodium intake and changes in body fluid volume. Expanded understanding of the role of the kidney as both a cause and target of hypertension highlights key aspects of pathophysiology and may lead to identification of new strategies for prevention and treatment., Introduction Hypertension is one of the most common chronic diseases of humankind, affecting more than 1 billion people worldwide (1). Although elevated blood pressure per se does not typically cause [...]

Angiotensin converting enzyme II (ACE2) is a component of the renin-angiotensin system (RAS) that negatively regulates angiotensin II (Ang II). Ang II, in turn, affects the expression of matrix metalloproteinases (MMPs) to induce heart remodeling. The specific mechanisms by which ACE2 regulates MMP-2, however, remain unclear. The aim of this study was to investigate the regulatory relationships between Ang II, ACE2, and MMP-2. ACE2 expression was upregulated and downregulated in human cardiofibroblasts (HCFs) by lentiviral infection. Effects on MMP-2 activity, shed ACE2 activity, extracellular signalregulated kinase (ERK) signaling pathway, and ADAM metallopeptidase domain 17 (ADAM17) expression were assessed. ACE2 increased MMP-2 activity, and Ang II inhibited this effect through the Ang II type-1 receptor (AT1R) and ERK1/2 signaling pathway. Ang II also reduced the effect of ACE2 on ERK1/2 levels, the activity of shed ACE2, and adam17 expression in HCFs. Additionally, these Ang II-mediated reductions could be attenuated by AT1R antagonist valsartan. In conclusion, these data help to clarify how ACE2 and Ang II interact to regulate MMP-2 and control tissue remodeling in heart disease. Key words: angiotensin II, angiotensin-converting enzyme II, matrix metalloproteinases-2, human cardiofibroblasts. L'enzyme de conversion de l'angiotensine II (ECA2) est une composante du systeme renine-angiotensine (SRA) qui regule negativement l'angiotensine II (Ang II). L'Ang II, elle, affecte l'expression des metalloproteases de la matrice (MMP) pour induire un remodelage cardiaque. Les mecanismes specifiques par lesquels l'ECA2 regule la MMP-2 demeurent cependant flous. Le but de cette etude etait d'examiner les relations regulatrices entre l'Ang II, l'ECA2 et la MMP-2. L'expression d'ECA2 a ete regulee a la hausse ou a la baisse par une infection lentivirale chez les fibroblastes cardiaques humains (FCH). Les effets sur l'activite de MMP-2, l'activite proteolytique d'ECA2, la voie signaletique de la kinase ERK et l'expression de ADAM17 ont ete evalues. L'ECA2 stimulait l'activite de la MMP-2, et l'Ang II inhibait cet effet par l'intermediaire du recepteur de l'Ang II de type 1 (AT1R) et de la voie signaletique de ERK1/2. L'Ang II reduisait aussi l'effet de l'ECA2 sur les niveaux de ERK1/2, l'activite proteolytique d'ECA2 et l'expression d'adam17 chez les FCH. De plus, ces reductions provoquees par l'Ang II pouvaient etre attenuees par le valsartan, un antagoniste du AT1R. En conclusion, ces donnees contribuent a clarifier comment l'ECA2 et l'Ang II interagissent pour reguler la MMP-2 et controler le remodelage tissulaire lors de maladies cardiaques. [Traduit par la Redaction] Mots-cles : angiotensine II, enzyme de conversion de l'angiotensine II, metalloprotease de la matrice-2, fibroblastes cardiaques humains., Introduction Angiotensin II (Ang II) is a main regulator of renin-angiotensin system (RAS) and functions to repair and remodel tissues by stimulating inflammation, cell growth, apoptosis, fibrogenesis, and differentiation (Ruiz-Ortega [...]

Branching morphogenesis of the ureteric bud (UB) is a key developmental process that controls organogenesis of the entire metanephros. Notably, aberrant UB branching may result in a spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). Genetic, biochemical and physiological studies have demonstrated that the renin-angiotensin system (RAS), a key regulator of the blood pressure and fluid/electrolyte homeostasis, also plays a critical role in kidney development. All the components of the RAS are expressed in the metanephros. Moreover, mutations in the genes encoding components of the RAS in mice or humans cause diverse types of CAKUT which include renal papillary hypoplasia, hydronephrosis, duplicated collecting system, renal tubular dysgenesis, renal vascular abnormalities, abnormal glomerulogenesis and urinary concentrating defect. Despite widely accepted role of the RAS in metanephric kidney and renal collecting system (ureter, pelvis, calyces and collecting ducts) development, the mechanisms by which an intact RAS exerts its morphogenetic actions are incompletely defined. Emerging evidence indicates that defects in UB branching morphogenesis may be causally linked to the pathogenesis of renal collecting system anomalies observed under conditions of aberrant RAS signaling. This review describes the role of the RAS in UB branching morphogenesis and highlights emerging insights into the cellular and molecular mechanisms whereby RAS regulates this critical morphogenetic process. Keywords Kidney development * Ureteric bud * Renin-angiotensin * GDNF * Ret * EGF receptor, Introduction Branching morphogenesis of the ureteric bud (UB) is a fundamental developmental process that controls organogenesis of the metanephros. Notably, derangements in UB morphogenesis cause a spectrum of congenital anomalies [...]

Accumulating evidence suggests that the intrarenal renin-angiotensin system may be involved in the progression of diabetic nephropathy. Chymase is a potent local angiotensin II-forming enzyme in several species, including humans and hamsters. However, the pathophysiological role of chymase is not fully understood. Here, we report a causal role of chymase in diabetic nephropathy and the therapeutic effectiveness of chymase inhibition. In the present study, renal chymase expression was markedly upregulated in streptozotocin-induced diabetic hamsters. Oral administration of a specific chymase inhibitor, TEI-F00806, completely ameliorated proteinuria, the overexpression of transforming growth factor-[beta] and fibronectin in glomeruli, and renal mesangial expansion, by normalizing the increase in intrarenal angiotensin II levels in diabetic hamsters independently of blood pressure levels. In contrast, ramipril did not show such sufficient effects. These effects occurred in parallel with improvements in superoxide production and expression of NAD(P)H oxidase components [NAD(P)H oxidase 4 and [p22.sup.phox]] in glomeruli. This study showed for the first time that chymase inhibition may protect against elevated intrarenal angiotensin II levels, oxidative stress, and renal dysfunction in diabetes. These findings suggest that chymase offers a new therapeutic target for diabetic nephropathy. angiotensin II; NAD(P)H oxidase doi: 10.1152/ajprenal.00337.2010

Endogenous and exogenous circulating ANG II acts at one of the central circumventricular organs (CVOs), the subfornical organ (SFO), to modulate chronic blood pressure regulation. However, at the forebrain, another important CVO is the organum vasculosum of the lamina terminalis (OVLT). In the present study, we tested the hypothesis that the OVLT mediates the hypertension or the hypotension produced by chronic infusion of ANG II or losartan (ATl antagonist), respectively. Six days after sham or OVLT electrolytic lesion, male Sprague-Dawley rats (280-320 g, n = 6 per group) were instrumented with intravenous catheters and radiotelemetric blood pressure transducers. Following another week of recovery, rats were given 3 days of saline control infusion (7 ml/day) and were then infused with ANG II (10 ng x [kg.sup.-1] x [min.sup.-1]) or losartan (10 mg x [kg.sup.-1] x [day.sup.-1]) for l0 days, followed by 3 recovery days. Twenty-four hour average measurements of mean arterial pressure (MAP) and heart rate (HR) were made during this protocol. Hydromineral balance (HB) responses were measured during the experimental protocol. By clay 9 of ANG II treatment, MAP had increased 16 [+ or -] 4 mmHg in sham rats but only 4 [+ or -] 1 mmHg in OVLT lesioned rats without changes in HR or HB. However, the hypotension produced by 10 days of losartan infusion was not modified in OVLT lesioned rats. These results suggest that the OVLT might play an important role during elevation of plasma ANG II, facilitating increases of blood pressure but is not involved with baseline effects of endogenous ANG II. hypertension; angiotensin II; losartan doi: 10.1152/ajpregu.00034.2010.

The role of angiotensin II (ANG II) in postnatal vasculogenesis and angiogenesis during skeletal muscle (SKM) regeneration is unknown. We examined the capacity of ANG II to stimulate capillary formation and growth during cardiotoxin-induced muscle regeneration in ACE inhibitor-treated ANG II type la receptor knockout ([AT1a.sup.-/-]) and C57Bl/6 control mice. Analysis of tibialis anterior (TA) cross-sections revealed 17% and 23% reductions in capillarization in [AT1a.sup.-/-] and captopril treated mice, respectively, when compared with controls, 21 days postinjury. Conversely, no differences in capillarization were detected at early time points (7 and 10 days). These results identify ANG II as a regulator of angiogenesis but not vasculogenesis in vivo. In vitro angiogenesis assays of human umbilical vein endothelial cells (HUVECs) further confirmed ANG II as proangiogeneic as 71% and 124% increases in tube length and branch point number were observed following ANG II treatment. Importantly, treatment of HUVECs with conditioned media from differentiated muscle cells resulted in an 84% and 203% increase in tube length and branch point number compared with controls, which was abolished following pretreatment of the cells with an angiotensin-converting enzyme inhibitor. The pro-angiogenic effect of ANG II can be attributed to an enhanced endothelial cell migration because both transwell and under agarose migration assays revealed a 37% and 101% increase in cell motility, respectively. Collectively, these data highlight ANG II as a proangiogenic regulator during SKM regeneration in vivo and more importantly demonstrates that ANG II released from SKM can signal endothelial cells and regulate angiogenesis through the induction of endothelial cell migration. captopril; migration; regeneration; vasculogenesis doi: 10.1152/ajpcell.00306.2010.

Angiotensin II (ANG II) contributes to hypertension, cardiac hypertrophy, fibrosis, and dysfunction; however, it is difficult to separate the cardiac effect of ANG II from its hemodynamic action in vivo. To overcome the limitations, we used transgenic mice with cardiac-specific expression of a transgene fusion protein that releases ANG II from cardiomyocytes (Tg-ANG II) and treated them with deoxycorticosterone acetate (DOCA)-salt to suppress their systemic renin-angiotensin system. Using this unique model, we tested the hypothesis that cardiac ANG II, acting on the angiotensin type 1 receptor ([AT.sub.1]R), increases inflammation, oxidative stress, and apoptosis, accelerating cardiac hypertrophy and fibrosis. Male Tg-ANG II mice and their non-transgenic littermates (n-Tg) were uninephrectomized and divided into the following three groups: 1) vehicle-treated normotensive controls; 2) DOCA-salt; and 3) DOCA-salt + valsartan ([AT.sub.1]R blocker). Under basal conditions, systolic blood pressure (SBP) and cardiac phenotypes were similar between strains. In DOCA-salt hypertension, SBP increased similarly in both n-Tg and Tg-ANG II, and cardiac function did not differ between strains; however, Tg-ANG II had 1) greater ventricular hypertrophy as well as interstitial and perivascular fibrosis; 2) a higher number of deoxynucleotidyl-transferase-mediated dUTP nick end labeling-positive cells and infiltrating macrophages; 3) increased protein expression of NADPH oxidase 2 and transforming growth factor-[[beta].sub.1]; and 4) downregulation of phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B (Akt) phosphorylation. Valsartan partially reversed these effects in Tg-ANG II but not in n-Tg. We conclude that, when hemodynamic loading conditions remain unchanged, cardiac ANG II does not alter heart size or cardiac functions. However, in animals with hypertension, cardiac ANG II, acting via [AT.sub.1]R, enhances inflammation, oxidative stress, and cell death (most likely via downregulation of PI 3-kinase and Akt), contributing to cardiac hypertrophy and fibrosis. inflammation; oxidative stress; cardiac hypertrophy; fibrosis doi: 10.1152/ajpheart.00538.2010.

It has been shown that angiotensin (ANG)-(1-7) activates nitric oxide synthase (NOS) in isolated ventricular myocytes from normotensive rats. Since many ANG-(1-7) actions are enhanced in situations of increased ANG II activity, as in hypertension, in this study we investigated the in vivo effect of ANG-(1-7) on NOS activity and expression of endothelial (eNOS), neuronal (nNOS), and inducible NOS (iNOS) in ventricles from spontaneously hypertensive rats (SHR). Rats were subjected to a 60-min ANG-(1-7) infusion (0.35 nmol/min); controls received saline. NOS activity was measured using the NADPH diaphorase histochemical method and by the conversion of L-[[sup.14]C]arginine to citrulline, and NOS phosphorylation and expression were determined using Western blotting. In SHR, ANG-(1-7) infusion diminished mean arterial pressure from 180 [+ or -] 9 to 146 [+ or -] 9 mmHg (P < 0.05), and this effect was prevented by nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor. In addition, NOS activity and eNOS phosphorylation were increased by ANG-(1-7) infusion. Ventricular eNOS and nNOS expression were increased 67.4 [+ or -] 6.4 and 51 [+ or -] 10%, respectively, by ANG-(1-7), whereas iNOS was not changed. In another set of experiments, we evaluated the mechanism by which ANG-(1-7) modifies NOS activity. Isolated ventricle slices preincubated with ANG-(1-7) showed an increase in NOS activity and eNOS phosphorylation, which was blocked by an [AT.sub.2] and a bradykinin [B.sub.2] receptor antagonist, but not by the Mas receptor antagonist. Our results show that in rats in a hypertensive state, ANG-(1-7) infusion upregulates cardiac NOS expression and activity through an [AT.sub.2]- and bradykinin-dependent mechanism. In this way ANG-(1-7) may eficit its cardioprotective action and contribute to some of the counterregulatory [AT.sub.2] receptor effects that oppose the [AT.sub.1] receptor-mediated effects. receptors; hypertension; heart; bradykinin doi: 10.1152/ajpheart.00850.2009.

The goals of this study were to 1) determine the acute effect of ANG-(1-7) on vascular tone in isolated middle cerebral arteries (MCAs) from Sprague-Dawley rats fed a normal salt (NS; 0.4% NaC1) diet, 2) evaluate the ability of chronic intravenous infusion of ANG-(1-7) (4 ng x [kg.sup.-1] x [min.sup.-l]) for 3 days to restore endothelium-dependent dilation to acetylcholine (ACh) in rats fed a high-salt (HS; 4% NaCl) diet, and 3) determine whether the amelioration of endothelial dysfunction by ANG-(1-7) infusion in rats fed a HS diet is different from the protective effect of low-dose ANG II infusion in salt-fed rats. MCAs from rats fed a NS diet dilated in response to exogenous ANG-(1-7) ([10.sup.-10] - [10.sup.-5] M). Chronic ANG-(1-7) infusion significantly reduced vascular superoxide levels and restored the nitric oxide-dependent dilation to ACh ([10.sup.-10]-[10.sup.-5] M) that was lost in MCAs of rats fed a HS diet. Acute vasodilation to ANG-(1-7) and the restoration of ACh-induced dilation by chronic ANG-(1-7) infusion in rats fed a HS diet were blocked by the Mas receptor antagonist [D-ALA(7)]-ANG-(1-7) or the ANG II type 2 receptor antagonist PD-123319 and unaffected by ANG II type 1 receptor blockade with losartan. The restoration of ACh-induced dilation in MCAs of HS-fed rats by chronic intravenous infusion of ANG II (5 ng x [kg.sup.-1] x [min.sup.-1]) was blocked by losartan and unaffected by D-ALA. These findings demonstrate that circulating ANG-(1-7), working via the Mas receptor, restores endothelium-dependent vasodilation in cerebral resistance arteries of animals fed a HS diet via mechanisms distinct from those activated by low-dose ANG II infusion. Mas receptor; nitric oxide; oxidative stress; angiotensin II doi: 10.1152/ajpheart.00328.2010.

The study was undertaken to examine the potential cross talk between vasopressin and angiotensin II (ANG II) intracellular signaling pathways. We investigated in vivo and in vitro whether vasopressin-induced water reabsorption could be attenuated by ANG II AT1 receptor blockade (losartan). On a low-sodium diet (0.5 meq/day) dDAVP-treated animals with or without losartan exhibited comparable renal function [creatinine clearance 1.2 [+ or -] 0.1 in dDAVP + losartan (LSDL) vs. 1.1 [+ or -] 0.1 ml x 100 [g.sup.-1] x [day.sup.-1] in dDAVP alone (LSD), P > 0.05] and renal blood flow (6.3 [+ or -] 0.5 in LSDL vs. 6.8 [+ or -] 0.5 ml/min in LSD, P > 0.05). The urine output, however, was significantly increased in LSDL (2.5 [+ or -] 0.2 vs. 1.8 [+ or -] 0.2 ml x 100 [g.sup.-l] x [day.sup.-1], P < 0.05) in association with decreased urine osmolality (2,600 [+ or -] 83 vs. 3,256 [+ or -] 110 mosmol/kg[H.sub.2]O, P < 0.001) compared with rats in LSD. Immunoblotting revealed significantly decreased expression of medullary AQP2 (46 [+ or -] 6 vs. 176 [+ or -] 10% in LSD, P < 0.01), p-AQP2 (177 [+ or -] 13 vs. 214 [+ or -] 12% in LSD, P < 0.05), and AQP3 (134 [+ or -] 14 vs. 177 [+ or -] 11% in LSD, P < 0.05) in LSDL compared with LSD. The expressions of AQP1, the [[alpha].sub.1]- and [gamma]-subunits of Na-K-ATPase, and the Na-K-2Cl cotransporter were not different among groups. In vitro studies showed that ANG II or dDAVP treatment was associated with increased AQP2 expression and cAMP levels, which were potentiated by cotreatment with ANG II and dDAVP and were inhibited by AT1 blockade. In conclusion, ANG II AT1 receptor blockade in dDAVP-treated rats on a low-salt diet was associated with decreased urine concentration and decreased inner medullary AQP2, p-AQP2, and AQP3 expression, suggesting that AT1 receptor activation plays a significant role in regulating aquaporin expression and modulating urine concentration in vivo. Studies in collecting duct cells were confirmatory. aquaporin; urine concentration; cAMP doi: 10.1152/ajprenal.00168.2010.

To accelerate lung development and protect neonates from other early developmental problems, synthetic steroids are administered maternally in the third trimester, exposing fetuses that are candidates for premature delivery to them. However, steroid exposure at this point of gestation may lead to elevated blood pressure [mean arterial pressure (MAP)] during adolescence. We hypothesize that fetal exposure to steroids activates the renin-angiotensin system, inducing an elevation in blood pressure and attenuation of baroreflex sensitivity (BRS) that is angiotensin II dependent in early adulthood. To test this hypothesis, fetal sheep were exposed to betamethasone (Beta) or vehicle (control) administered to ewes at day 80 of gestation and delivered at full term. At 1.8 yr of age, male offspring were instrumented for conscious recording of MAP, heart rate, and measurement of BRS [as low-frequency-[alpha], high-frequency-co, sequence (seq) UP, seq DOWN, and seq TOTAL]. Beta-exposed sheep (n = 6) had higher MAP than control sheep (n = 5) (93 [+ or -] 2 vs. 84 [+ or -] 2 mmHg, P < 0.01). Acute blockade of angiotensin type 1 receptors with candesartan (0.3 mg/kg iv) normalized MAP in Beta-exposed sheep (85 [+ or -] 4 mmHg), with no effect in control sheep (82 [+ or -] 3 mmHg). Before angiotensin type 1 blockade, BRS maximum gain was significantly lower in Beta-exposed vs. control sheep (11 [+ or -] 3 vs. 26 [+ or -] 3 ms/mmHg, P < 0.0.01). However, 45 min after candesartan injection, BRS was increased in Beta-exposed (21 [+ or -] 5 ms/mmHg) and control (35 [+ or -] 4 ms/mmHg) sheep. Heart rate variability (HRV) and blood pressure variability (BPV) revealed lower HRV (SD of beat-to-beat interval and root mean square of successive beat-to-beat differences in R-R interval duration) and higher BPV (SD of MAP, systolic arterial pressure in low-frequency range) in Beta-exposed sheep. Candesartan partially restored HRV in Beta-exposed sheep and fully corrected BPV. Thus, in utero exposure to synthetic glucocorticoids causes long-lasting programming of the cardiovascular system via renin-angiotensin system-dependent mechanisms. spectral analysis; fetal programming; heart rate variability; blood pressure variability; renin-angiotensin system; hypertension doi: 10.1152/ajpheart.00100.2010.

An increase in plasma ANG II causes neuronal activation in hypothalamic nuclei and a slow pressor response, presumably by increasing sympathetic drive. We evaluated whether the activation of a neuromodulatory pathway, involving aldosterone and 'ouabain,' is involved in these responses. In Wistar rats, the subcutaneous infusion of ANG II at 150 and 500 ng x [kg.sup.-1] x [min.sup.-1] gradually increased blood pressure up to 60 mmHg at the highest dose. ANG II at 500 ng x [kg.sup.-1] x min increased plasma ANG II by 4-fold, plasma aldosterone by 25-fold, and hypothalamic aldosterone by 3-fold. The intracerebroventricular infusion of an aldosterone synthase (AS) inhibitor prevented the ANG II-induced increase in hypothalamic aldosterone without affecting the increase in plasma aldosterone. Neuronal activity, as assessed by Fra-like immunoreactivity, increased transiently in the subfornical organ (SFO) but progressively in the paraventricular nucleus (PVN) and supraoptic nucleus (SON). The central infusion of the AS inhibitor or a mineralocorticoid receptor blocker markedly attenuated the ANG II-induced neuronal activation in the PVN but not in the SON. Pressor responses to ANG II at 150 ng x [kg-] x [min.sup.-1] were abolished by an intracerebroventricular infusion of the AS inhibitor. Pressor responses to ANG II at 500 ng x [kg.sup.-1] x [min.sup.-1 were attenuated by the central infusion of the AS inhibitor or the mineralocorticoid receptor blocker by 70-80% and by Digibind (to bind 'ouabain') by 50%. These results suggest a novel central nervous system mechanism for the ANG II-induced slow pressor response, i.e., circulating ANG II activates the SFO, leading to the direct activation of the PVN and SON, and, in addition, via aldosterone-dependent amplifying mechanisms, causes sustained activation of the PVN and thereby hypertension. Fra-like immunoreactivity; aldosterone synthase inhibitor; eplerenone; telemetry; angiotensin II doi: 10.1152/ajpheart.00256.2010.

Podocytes are an integral and important constituent of the glomerular filtration barrier (GFB) and are exposed to a higher concentrations of ANG II in diseased states; consequently, podocytes may accumulate oxidized proteins and damaged mitochondria. In the present study, we evaluated the effect of ANG II on the podocyte autophagic process, which is likely to be triggered in order to degrade unwanted proteins and damaged organelles. To quantitate the occurrence of autophagy, electron microscopic studies were carried out on control and ANG II-treated conditionally immortalized mouse podocytes (CIMPs). ANG II-treated cells showed a fivefold greater number of autophagosomes/field compared with control cells. This proautophagic effect of ANG II was inhibited by pretreatment with 3-methyladenine, an inhibitor of autophagy. ANG II also enhanced podocyte expression of autophagic genes such as LC3-2 and beclin-1. Since oxidative stress is often associated with the induction of autophagy, we examined the effect of ANG II on podocyte reactive oxygen species (ROS) generation. ANG II enhanced podocyte ROS generation in a time-dependent manner. To determine whether there is a causal relationship between ANG II-induced oxidative stress and induction of autophagy, we evaluated the effect of antioxidants on ANG II-induced autophagy. As expected, the proautophagic effect of ANG II was inhibited by antioxidants. We conclude that ANG II promotes podocyte autophagy through the generation of ROS. oxidative stress; angiotensin II doi: 10.1152/ajpcell.00424.2009.

We examined the mechanisms that maintain stable renal tissue [Po.sub.2] during moderate renal ischemia, when changes in renal oxygen delivery ([??]o.sub.2]) and consumption ([[??]o.sub.2]) are mismatched. When renal artery pressure (RAP) was reduced progressively from 80 to 40 mmHg, [[??]o.sub.2] (-38 [+ or -] 7%) was reduced more than [Do.sub.2] (-26 [+ or -] 4%). Electrical stimulation of the renal nerves (RNS) reduced [Do.sub.2] (-49 [+ or -] 4% at 2 Hz) more than [[??]o.sub.2] (-30 [+ or -] 7% at 2 Hz). Renal arterial infusion of angiotensin II reduced [Do.sub.2] (-38 [+ or -] 3%) but not [[??]o.sub.2] (+ 10 [+ or -] 10%). Despite mismatched changes in [[??]o.sub.2] and [[??]o.sub.2], renal tissue [Po.sub.2] remained remarkably stable at [greater than or equal to] 40 mmHg RAP, during RNS at [less than or equal to] 2 Hz, and during angiotensin II infusion. The ratio of sodium reabsorption to [[??]o.sub.2] was reduced by all three ischemic stimuli. None of the stimuli significantly altered the gradients in P[co.sub.2] or pH across the kidney. Fractional oxygen extraction increased and renal venous Po2 fell during 2-Hz RNS and angiotensin II infusion, but not when RAP was reduced to 40 mmHg. Thus reduced renal [[??]o.sub.2] can help. prevent tissue hypoxia during mild renal ischemia, but when renal [[??]o.sub.2] is reduced less than [[??]o.sub.2], other mechanisms prevent a fall in renal [Po.sub.2]. These mechanisms do not include increased efficiency of renal oxygen utilization for sodium reahsorption or reduced washout of carbon dioxide from the kidney, leading to increased oxygen extraction. However, increased oxygen extraction could be driven by altered countercurrent exchange of carbon dioxide and/or oxygen between renal arteries and veins. angiotensin II; carbon dioxide; hypoxia; hypotension; oxygen; sympathetic nervous system doi: 10.1152/ajprenal.00647.2009

Inflammatory factors are elevated in animal and human subjects with hypertension and renal injury. We hypothesized that inflammation contributes to hypertension-induced renal injury by impairing autoregulation and microvascular reactivity to [P2X.sub.1] receptor activation. Studies were conducted in vitro using the blood-perfused juxtamedullary nephron preparation. Rats receiving ANG II (60 ng/min) infusion were treated with the anti-inflammatory agent pentosan polysulfate (PPS) for 14 days. The magnitude and progression of hypertension were similar in ANG II and ANG II+PPS-treated rats (169 [+ or -] 5 vs. 172 [+ or -] 2 mmHg). Afferent arterioles from control rats exhibited normal autoregulatory behavior with diameter decreasing from 18.4 [+ or -] 1.6 to 11.4 [+ or -] 1.7 [micro]m when perfusion pressure was increased from 70 to 160 mmHg. In contrast, pressure-mediated vasoconstriction was markedly attenuated in ANG II-treated rats, and diameter remained essentially unchanged over the range of perfusion pressures. However, ANG II-treated rats receiving PPS exhibited normal autoregulatory behavior compared with ANG II alone rats. Arteriolar reactivity to ATP and [beta],[gamma]-methylene ATP was significantly reduced in ANG II hypertensive rats compared with controls. Interestingly, PPS treatment preserved normal reactivity to P2 and [P2X.sub.1] receptor agonists despite the persistent hypertension. The maximal vasoconstriction was 79 [+ or -] 3 and 81 [+ or -] 2% of the control diameter for ATP and [beta], [gamma]-methylene ATP, respectively, similar to responses in control rats. PPS treatment significantly reduced [alpha]-smooth muscle actin staining in afferent arterioles and plasma transforming growth factor-[beta]1 concentration in ANG II-treated rats. In conclusion, PPS normalizes autoregulation without altering ANG II-induced hypertension, suggesting that inflammatory processes reduce [P2X.sub.1] receptor reactivity and thereby impair autoregulatory behavior in ANG II hypertensive rats. [P2X.sub.1] purinoceptor; afferent arteriole; pentosan polysulfate doi: 10.1152/ajprenal.00743.2009.

Placental insufficiency results in intrauterine growth restriction (IUGR) and hypertension in adult male growth-restricted rats. Although renal ANG II and plasma renin activity do not differ between growth-restricted and control rats, blockade of the renin-angiotensin system (RAS) abolishes hypertension in growth-restricted rats, suggesting that the RAS contributes to IUGR-induced hypertension. Moreover, castration abolishes hypertension in growth-restricted rats, indicating an important role for testosterone. Therefore, we hypothesized that enhanced responsiveness to ANG II contributes to hypertension in this model of IUGR and that androgens may play a pivotal role in this enhanced response. Physiological parameters were determined at 16 wk of age in male rats pretreated with enalapril (40 mg x [kg.sup.-1] x [day.sup.-1]) for 1 wk. Baseline blood pressures were similar between growthrestricted (112 [+ or -] 3 mmHg) and control (110 [+ or -] 2 mmHg) rats; however, an enhanced pressor response to acute ANG II (100 ng x [kg.sup.-1] x [min.sup.-1] for 30 min) was observed in growth-restricted (160 [+ or -] 2 mmHg) vs. control (136 [+ or -] 2 mmHg; P < 0.05) rats. Castration abolished the enhanced pressor response to acute ANG II in growth-restricted (130 [+ or -] 2 mmHg) rats with no significant effect on blood pressure in controls (130 [+ or -] 2 mmHg). Blood pressure was increased to a similar extent above baseline in response to acute phenylephrine (100 [micro]g/min) in control (184 [+ or -] 5 mmHg) and growth-restricted (184 [+ or -] 8 mmHg) rats, suggesting the enhanced pressor response in growth-restricted rats is ANG II specific. Thus, these results suggest that growth-restricted rats exhibit an enhanced responsiveness to ANG II that is testosterone dependent and indicate that the RAS may serve as an underlying mechanism in mediating hypertension programmed in response to IUGR. sex steroids; blood pressure; developmental programming doi: 10.1152/ajpregu.00096.2010.

Angiotensin-(1-7) [ANG-(1-7)], one of the bioactive peptides produced in the renin-angiotensin system, plays a pivotal role in cardiovascular physiology by providing a counterbalance to the function of ANG II. Recently, it has been considered as a potential candidate for therapeutic use in the treatment of various types of cardiovascular diseases. The aim of the present study is to explain the modulatory role of ANG-(1-7) in atrial natriuretic peptide (ANP) secretion and investigate the functional relationship between two peptides to induce cardiovascular effects using isolated perfused beating rat atria and a cardiac hypertrophied rat model. ANG-(1-7) (0.01, 0.1, and 1 [micro]M) increased ANP secretion and ANP concentration in a dose-dependent manner at high atrial pacing (6.0 Hz) with increased cGMP production. However, at low atrial pacing (1.2 Hz), ANG-(1-7) did not cause changes in atrial parameters. Pretreatment with an antagonist of the Mas receptor or with inhibitors of phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), or nitric oxide synthase blocked the augmentation of high atrial pacing-induced ANP secretion by ANG-(1-7). A similar result was observed with the inhibition of the [Na.sup.+]/[H.sup.+] exchanger-1 and [Ca2.sup.+]/ calmodulin-dependent kinase II (CaMKII). ANG-(1-7) did not show basal intracellular [Ca2.sup.+] signaling in quiescent atrial myocytes. In an in vivo study using an isoproterenol-induced cardiac hypertrophy animal model, an acute infusion of ANG-(1-7) increased the plasma concentration of ANP by twofold without changes in blood pressure and heart rate. A chronic administration of ANG-(1-7) increased the plasma ANP level and attenuated isoproterenol-induced cardiac hypertrophy. The antihypertrophic effect was abrogated by a cotreatment with the natriuretic peptide receptor-A antagonist. These results suggest that 1) ANG-(1-7) increased ANP secretion at high atrial pacing via the Mas/PI3K/Akt pathway and the activation of [Na.sup.+]/[H.sup.+] exchanger-1 and CaMKII and 2) ANG-(1-7) decreased cardiac hypertrophy which might be mediated by ANP. atrial natriuretic peptide; cardiac hypertrophy; atrial myocyte; Mas; signal transduction: phosphatidylinositol 3-kinase doi: 10.1152/ajpheart.00608.2009.

Araujo M, Welch WJ. Tubuloglomerular feedback is decreased in COX-1 knockout mice after chronic angiotensin II infusion. Am J Physiol Renal Physiol 298: F1059-F1063, 2010. First published January 27, 2010; doi: 10.1152/ajprenal.00547.2009.--Prostaglandins (PGs), produced by two isoforms of cyclooxygenase (COX), COX-1 and COX-2, are important modulators of renal hemodynamics. COX-1 and COX-2 are expressed in the kidney often at distinct sites. Thromboxane ([TxA.sub.2]), [PGE.sub.2], and prostacyclin (PGI2) are the major PGs in the renal cortex of mice. Acute infusion of the vasoconstrictor ANG II increases COX-2-dependent [PGE.sub.2] and [PGI.sub.2]. COX-2 is primarily expressed in the macula densa (MD), where several PG synthases are also expressed. We previously showed that MD COX-2 products modulate tubuloglomerular feedback (TGF) in the rat. Genetic deletion of COX-1 enhances COX-2 production of PGs, decreases renal and urinary PGs, and attenuates ANG II-induced hypertension. The present study tested the effects of chronic ANG II infusion on TGF in COX-1 knockout (KO) mice. Basal TGF was similar in COX-1 KO and wild-type (WT) mice. Chronic ANG II infusion increased TGF in WT mice (WT: 9.3 [+ or -] 0.7 vs. WT + ANG II: 12.2 [+ or -] 1.6 mmHg, P < 0.02). However, chronic ANG II decreased TGF in COX-1 KO mice (KO: 11.4 [+ or -] 1.1 vs. KO + ANG II: 8.3 [+ or -] 0.6 mmhg, P < 0.01). Pretreatment with the COX-2 inhibitor SC58,236 in COX-1 KO mice prevented the ANG II-associated reduction in TGF (11.4 [+ or -] 1.0 vs. 11.5 [+ or -] 0.28 mmHg, not significant). Excretion of 6-keto-[PGF.sub.2[alpha]], the metabolite of PGI2, was increased by ANG II infusion, whereas excretion of TxB2, the stable metabolite of [TxA.sub.2], was not changed. ANG II infusion increased mean arterial pressure similarly in both WT and KO mice (WT: 93 [+ or -] 2 vs. KO: 92 [+ or -] 3 mmHg), but not in KO mice pretreated with SC-58,236 (85 [+ or -] 2 mmHg). This study shows that COX-l-generated PGs partially mediate ANG II increases in TGF and that COX-2 PGs offset that effect. cyclooxygenase; prostaglandins; hypertension doi: 10.1152/ajprenal.00547.2009.

Contag SA, Bi J, Chappell MC, Rose JC. Developmental effect of antenatal exposure to betamethasone on renal angiotensin H activity in the young adult sheep. Am J Physiol Renal Physiol 298: F847-F856, 2010. First published January 13, 2010; doi:10.1152/ajprenal.00497.2009.--Antenatal corticosteroids may have long-term effects on renal development which have not been clearly defined. Our objective was to compare the responses to intrarenal infusions of ANG II in two groups of year-old, male sheep: one group exposed to a clinically relevant dose of betamethasone before birth and one not exposed. We wished to test the hypothesis that antenatal steroid exposure would enhance renal responses to ANG II in adult life. Six pairs of male sheep underwent unilateral nephrectomy and renal artery catheter placement. The sheep were infused for 24 h with ANG II or with ANG II accompanied by blockade of the angiotensin type 1 (A[T.sub.1]) or type 2 (AT2) receptor. Baseline mean arterial blood pressure among betamethasone-exposed sheep was higher than in control animals (85.8 [+ or -] 2.2 and 78.3 [+ or -] 1.0 mmHg, respectively, P = 0.003). Intrarenal infusion of ANG II did not increase systemic blood pressure (P [greater than or equal to] 0.05) but significantly decreased effective renal plasma flow and increased renal artery resistance (P < 0.05). The decrease in flow and increase in resistance were significantly greater in betamethasone- compared with vehicleexposed sheep (betamethasone P < 0.05, vehicle P [greater than or equal to] 0.05). This effect appeared to be mediated by a heightened sensitivity to the A[T.sub.1] receptor among betamethasone-exposed sheep. Sodium excretion initially decreased in both groups during ANG II infusion; however, a rebound was observed after 24 h. A[T.sub.1] blockade was followed by a significant rebound after 24 h in both groups. A[T.sub.2] blockade blunted the 24-h rebound effect among the vehicle-exposed sheep compared with the betamethasone-exposed sheep. In conclusion, antenatal corticosteroid exposure appears to modify renal responsiveness to ANG II by increasing A[T.sub.1]- and decreasing A[T.sub.2] receptor-mediated actions particularly as related to renal blood flow and sodium excretion. angiotensin receptor; renal plasma flow; glomerular filtration rate; corticosteroids doi: 10.1152/ajprenal.00497.2009.

Crowley SD, Song Y, Lin EE, Griffiths R, Kim H, Ruiz P. Lymphocyte responses exacerbate angiotensin H-dependent hypertension. Am J Physiol Regul Integr Comp Physiol 298: R1089-R1097, 2010. First published February 10, 2010; doi:10.1152/ajpregu.00373.2009.--Activation of the immune system by ANG II contributes to the pathogenesis of hypertension, and pharmacological suppression of lymphocyte responses can ameliorate hypertensive end-organ damage. Therefore, to examine the mechanisms through which lymphocytes mediate blood pressure elevation, we studied ANG II-dependent hypertension in scid mice lacking lymphocyte responses and wild-type controls. Scid mice had a blunted hypertensive response to chronic ANG II infusion and accordingly developed less cardiac hypertrophy. Moreover, lymphocyte deficiency led to significant reductions in heart and kidney injury following 4 wk of angiotensin. The muted hypertensive response in the scid mice was associated with increased sodium excretion, urine volumes, and weight loss beginning on day 5 of angiotensin infusion. To explore the mechanisms underlying alterations in blood pressure and renal sodium handling, we measured gene expression for vasoactive mediators in the kidney after 4 wk of ANG II administration. Scid mice and controls had similar renal expression for interferon-[gamma], interleukin-1[beta], and interleukin-6. By contrast, lymphocyte deficiency (i.e., scid mice) during ANG II infusion led to upregulation of tumor necrosis factor-[alpha], endothelial nitric oxide synthase (eNOS), and cyclooxygenase-2 (COX-2) in the kidney. In turn, this enhanced eNOS and COX-2 expression in the scid kidneys was associated with exaggerated renal generation of nitric oxide, prostaglandin [E.sub.2], and prostacyclin, all of which promote natriuresis. Thus, the absence of lymphocyte activity protects from hypertension by allowing blood pressure-induced sodium excretion, possibly via stimulation of eNOSand COX-2-dependent pathways. inflammation; kidney diseases; T lymphocytes doi: 10.1152/ajpregu.00373.2009.

Previous studies have shown that in proximal and distal tubule nephron segments, peritubular ANG II stimulates sodium chloride transport. However, ANG II inhibits chloride transport in the medullary thick ascending limb (mTAL). Because ANG II and catecholamines are both stimulated by a decrease in extracellular fluid volume, the purpose of this study was to examine whether there was an interaction between ANG II and catecholamines to mitigate the inhibition in chloride transport by ANG II. In isolated perfused rat mTAL, [10.sup.-8] M bath ANG II inhibited wansport (from a basal transport rate of 165.6 [+ or -] 58.8 to 58.8 [+ or -] 29.4 pmol*[mm.sup.-1]*[min.sup.-1]; p < 0.0l). Bath norepinephrine stimulated chloride transport (from a basal transport rate of 298.1 [+ or -] 31.7 to 425.2 [+ or -] 45.8 pmol*[mm.sup.-1]*[min.sup.-1]; P < 0.05) and completely prevented the inhibition in chloride transport by ANG II. The stimulation of chloride transport by norepinephrine was mediated entirely by its [beta]-adrenergic effect; however, both the [beta]- and [alpha]-adrenergic agonists isoproterenol and phenylephrine prevent the ANG II-mediated inhibition in chloride transport. In the presence of [10.sup.-5] M propranolol, the effect of norepinephrine to prevent the inhibition of chloride transport by ANG II was still present. These data are consistent with an interaction of both [alpha]- and [beta]-catecholamines and ANG II on net chloride transport in the mTAL. NKCC2; norepinephrine; isoproterenol doi: 10.1152/ajpregu.00758.2009.

ANG II [AT.sub.2] receptor ([AT.sub.2]R)-deficient mice exhibit abnormal ureteric bud (UB) budding, increased incidence of double ureters, and vesicoureteral reflux. However, the role of the [AT.sub.2]R during UB morphogenesis and the mechanisms by which aberrant [AT.sub.2]R signaling disrupts renal collecting system development have not been fully defined. In this study, we mapped the expression of the [AT.sub.2]R during mouse metanephric development, examined the impact of disrupted [AT.sub.2]R signaling on UB branching, cell proliferation, and survival, and investigated the cross talk of the [AT.sub.2]R with the glial-derived neurotrophic factor (GDNF)/c-Ret/Wnt11 signaling pathway. Embryonic mouse kidneys express [AT.sub.2]R in the branching UB and the mesenchyme. Treatment of embryonic day 12.5 (El2.5) metanephroi with the [AT.sub.2]R antagonist PD123319 or genetic inactivation of the [AT.sub.2]R in mice inhibits UB branching, decreasing the number of UB tips compared with control (34 [+ or -] 1.0 vs. 43 [+ or -] 0.6, P < 0.01; 36 [+ or -] 1.8 vs. 48 [+ or -] 1.3, P < 0.01, respectively). In contrast, treatment of metanephroi with the [AT.sub.2]R agonist CGP42112 increases the number of UB tips compared with control (48 [+ or -] 1.8 vs. 39 [+ or -] 12.3, P < 0.05). Using real-time quantitative RT-PCR and whole mount in situ hybridization, we demonstrate that PD 123319 downregulates the expression of GDNF, c-Ret, Wnt11, and Spryl mRNA levels in E12.5 metanephroi grown ex vivo. [AT.sub.2]R blockade or genetic inactivation of [AT.sub.2]R stimulates apoptosis and inhibits proliferation of the UB cells in vivo. We conclude that [AT.sub.2]R performs essential functions during UB branching morphogenesis via control of the GDNF/c-Ret/Wnt11 signaling pathway, UB cell proliferation, and survival. angiotensin; GDNF; c-Ret doi:10.1152/ajprenal.00147.2009

Recent studies have shown that asymmetric dimethylarginine (ADMA), a nitric oxide synthase inhibitor, is increased in hypertension and chronic kidney disease. However, little is known about the effects of hypertension per se on ADMA metabolism. The purpose of this study was to test the hypothesis that ANG II-induced hypertension, in the absence of renal injury, is associated with increased oxidative stress and plasma and renal cortex ADMA levels in rats. Male Sprague-Dawley rats were treated with ANG II at 200 ng x [kg.sup.-1] x [min.sup.-1] sc (by minipump) for 1 or 3 wk or at 400 ng x [kg.sup.-1] x [min.sup.-1] for 6 wk. Mean arterial pressure was increased after 3 and 6 wk of ANG II; however, renal injury (proteinuria, glomerular sclerosis, and interstitial fibrosis) was only evident after 6 wk of treatment. Plasma thiobarbituric acid reactive substances concentration and renal cortex [p22.sup.phox] protein abundance were increased early (1 and 3 wk), but urinary excretion of isoprostane and [H.sub.2][O.sub.2] was only increased after 6 wk of ANG II. An increased in plasma ADMA after 6 wk of ANG II was associated with increased lung protein arginine methyltransferase-1 abundance and decreased renal cortex dimethylarginine dimethylaminohydrolase activity. No changes in renal cortex ADMA were observed. ANG II hypertension in the absence of renal injury is not associated with increased ADMA; however, when the severity and duration of the treatment were increased, plasma ADMA increased. These data suggest that elevated blood pressure alone, for up to 3 wk, in the absence of renal injury does not play an important role in the regulation of ADMA. However, the presence of renal injury and sustained hypertension for 6 wk increases ADMA levels and contributes to nitric oxide deficiency and cardiovascular disease. kidney; protein arginine methyltransferase-1; dimethylarginine dimethylaminohydrolase; oxidative stress doi:10.1152/ajpregu.90875.2008

Macula densa (MD)-mediated regulation of renal hemodynamics via tubuloglomerular feedback is regulated by interactions between factors such as superoxide ([O.sup.-.sub.2]) and angiotensin II (ANG II). We have reported that NaCl-induced [O.sup.-.sub.2] in the MD is produced by the NOX2 isoform of NADPH oxidase (NOX); however, the source of ANG II-induced [O.sup.-.sub.2] in MD is unknown. Thus we determined the pathways by which ANG II increased [O.sup.-.sub.2] in the MD by measuring [O.sup.-.sub.2] in ANG II-treated MMDD1 cells, a MD-like cell line. ANG II caused MMDD1 [O.sup.-.sub.2] levels to increase by more than twofold (P < 0.01). This increase was blocked by losartan ([AT.sub.1] receptor blocker) but not PD-123319 ([AT.sub.2] receptor antagonist). Apocynin (a NOX inhibitor) decreased [O.sup.-.sub.2] by 86% (P < 0.01), whereas oxypurinol (a xanthine oxidase inhibitor) and NS-398 (a cyclooxygenase-2 inhibitor) had no significant effect. The NOX-dependent increase in [O.sup.-.sub.2] was due to the NOX2 isoform; a short interfering (si)RNA against NOX2 blunted ANG II-induced increases in [O.sup.-.sub.2], whereas the NOX4/siRNA did not. Finally, we found that inhibiting the Rac1 subunit of NOX blunted ANG II-induced [O.sup.-.sub.2] production in NOX4/siRNA-treated cells but did not further decrease it in NOX2/siRNA-treated cells. Our results indicate that ANG II stimulates [O.sup.-.sub.2] production in the MD primarily via [AT.sub.1]-dependent activation of NOX2. Rac1 is required for the full activation of NOX2. This pathway may be an important component of ANG II enhancement of tubuloglomerular feedback. NAD(P)H oxidase; isoforms; tubuloglomerular feedback doi:10.1152/ajpregu.00762.2009

The present study examined whether chronic treatment with angiotensin (ANG)-(1-7) reduces cardiac remodeling and inhibits growth-promoting signaling pathways in the heart of fructose-fed rats (FFR), an animal model of insulin resistance. Sprague-Dawley rats were fed either normal rat chow (control) or the same diet plus 10% fructose in drinking water. For the last 2 wk of a 6-wk period of the corresponding diet, control and FFR were implanted with osmotic pumps that delivered ANG-(1-7) (100 ng x [kg.sup.-1] x [min.sup.-1]). A subgroup of each group of animals (control or FFR) underwent a sham surgery. We determined heart weight, myocyte diameter, interstitial fibrosis, and perivascular collagen type III deposition as well as the phosphorylation degree of ERK1/2, JNK1/2, and p38MAPK. FFR showed a mild hypertension that was significantly reduced after ANG-(1-7) treatment. Also, FFR displayed higher ANG II circulating and local levels in the heart that remained unaltered after chronic ANG-(1-7) infusion. An increased heart-to-body weight ratio, myocyte diameter, as well as left ventricular fibrosis and perivascular collagen type III deposition were detected in the heart of FFR. Interestingly, significant improvements in these cardiac alterations were obtained after ANG-(1-7) treatment. Finally, FFR that received ANG-(1-7) chronically displayed significantly lower phosphorylation levels of ERK1/2, JNK1/2, and p38MAPK. The beneficial effects obtained by ANG-(1-7) were associated with normal values of Src-homology 2-containing protein-tyrosine phosphatase-1 (SHP-1) activity in the heart. In conclusion, chronic ANG-(1-7) treatment ameliorated cardiac hypertrophy and fibrosis and attenuated the growth-promoting pathways in the heart. These findings show an important protective role of ANG-(1-7) in the heart of insulin-resistant rats. mitogen-activated protein kinase pathways; hypertension; left ventricular fibrosis doi:10.1152/ajpheart.00803.2009

Neuropeptide Y (NPY) is a cotransmitter with norepinephrine (NE) and ATP in sympathetic nerves. There is evidence for increased activity of the sympathetic nervous system and the renin-angiotensin system (RAS), as well as a role for NPY in the development of hypertension in experimental animal models and in humans. Angiotensin II (ANG II) is known to facilitate sympathetic neurotransmission, an effect greater in spontaneously hypertensive rats (SHR) than normotensive Wistar-Kyoto (WKY) rats. A newly discovered product of the RAS is angiotensin-(1-7) [ANG-(I-7)]. There is evidence suggesting that ANG-(1-7) opposes the actions of ANG II, resulting in hypotensive effects. The objective of this study was to investigate the role of ANG-(1-7) on the nerve-stimulated overflow of NE and NPY from the mesenteric arterial bed of SHR and the mechanisms involved in mediating any effects produced. ANG-(1-7) (0.001, 0.01, 0.1 [micro]M) decreased nerve-stimulated NE and NPY overflow, as well as perfusion pressure in preparations obtained from SHR. This effect was greater in preparations of SHR than WKY controls. In addition, ANG-(1-7) decreased NE overflow to a greater extent than NPY overflow. Administration of the Mas receptor antagonist, D-Ala7 ANG-(1-7), attenuated the decrease in both NE and NPY overflow due to ANG-(1-7) administration. However, the angiotensin type 2 receptor antagonist, PD-123391, attenuated the effect of ANG-(1-7) on NE overflow without affecting the decrease in NPY overflow. Moreover, in the presence of [N.sup.G]-nitro-L-arginine methyl ester, ANG(1-7) decreased NPY overflow, but not NE overflow. ANG-(1-7) decreases the nerve-stimulated overflow of NE and NPY in preparations of SHR, whereas ANG II enhances it. Therefore, ANG-(I-7) may counteract the effects of ANG II by acting on ANG type 2 and Mas receptors. sympathetic neurotransmission; nitric oxide; bradykinin; mesenteric artery doi: 10.1152/ajpheart.00400.2009

Mizushima T, Sasaki M, Ando T, Wada T, Tanaka M, Okamoto Y, Ebi M, Hirata Y, Murakami K, Mizoshita T, Shimura T, Kubota E, Ogasawara N, Tanida S, Kataoka H, Kamiya T, Alexander JS, Joh T. Blockage of angiotensin II type 1 receptor regulates TNF-[alpha]-induced MAdCAM-1 expression via inhibition of NF-[kappa]B translocation to the nucleus and ameliorates colitis. Am J Physiol Gastrointest Liver Physiol 298: G255-G266, 2010. First published November 25, 2009; doi: 10.1152/ajpgi.00264.2009.-- Mucosal vascular addressin cell adhesion molecule 1 (MAdCAM-1) is an important target in the treatment of inflammatory bowel disease (1BD). Recently, treatment of IBD with an antibody to [alpha]4137-integrin, a ligand for MAdCAM-1, has been an intense focus of research. Our aim was to clarify the mechanism by which MAdCAM-1 is regulated via angiotensin II type 1 receptor (AT1R), and to verify if AT1R might be a novel target for IBD treatment. The role of AT1R in the expression of MAdCAM-1 in SVEC (a murine high endothelial venule cell) and MJC-1 (a mouse colonic endothelial cell) was examined following cytokine stimulation. We further evaluated the effect of AT1R on the pathogenesis of immunemediated colitis using AT1R-deficient (AT1R-/-) mice and a selective AT1R blocker. AT1R blocker significantly suppressed MAdCAM-1 expression induced by TNF-[alpha], but did not inhibit phosphorylation of p38 MAPK or of I[kappa]B that modulate MAdCAM-1 expression. However, NF-[kappa]B translocation into the nucleus was inhibited by these treatments. In a murine colitis model induced by dextran sulfate sodium, the degree of colitis, judged by body weight loss, histological damage, and the disease activity index, was much milder in AT1R-/- than in wild-type mice. The expression of MAdCAM-I was also significantly lower in AT1R-/- than in wild-type mice. These results suggest that AT1R regulates the expression of MAdCAM-1 under colonic inflammatory conditions through regulation of the translocation of NF-[kappa]B into the nucleus. Furthermore, inhibition of ATIR ameliorates colitis in a mouse colitis model. Therefore, AT1R might be one of new therapeutic target of IBD via regulation of MAdCAM-1. mucosal addressin cell adhesion molecule-l; inflammatory bowel disease; nuclear factor-[kappa]B doi: 10.1152/ajpgi.00264.2009

Hyperglycemia-associated glucotoxicity induces [beta]-cell apoptosis but the underlying mechanisms are unknown. Interestingly, prolonged exposure to high glucose upregulates the expression and function of the renin-angiotensin system (RAS). We hypothesize that the voltagegated outward potassium ([K.sub.v]) current, which governs [beta]-cell membrane potential and insulin secretion, has a role in glucotoxicity. In this study, we investigated the effects of prolonged exposure to high glucose on mouse pancreatic [beta]-cells and concurrent effects on the RAS by examining changes in expression of angiotensin II (ANG II) receptors and changes in the expression and activity of [K.sub.v] channels. [beta]-Cells were incubated in high glucose medium for 1-7 days and then were examined with electrophysiological and molecular biology techniques. Prolonged exposure to high glucose produced a marked increase in [beta]-cell primary [K.sub.v] channel subunit, [K.sub.v]2.1, expression and [K.sub.v] current amplitude. Enhanced expression of ANG II type 1 receptor ([AT.sub.1]R) was also observed under high glucose conditions, whereas blockade of [AT.sub.1]R by losartan did not alter [K.sub.v] channel expression. External application of ANG II reduced [K.sub.v] current amplitude under normal, but not high, glucose conditions. The effect of ANG II on [K.sub.v] channel gating was abolished by ANG II type 2 receptor ([AT.sub.2]R) antagonism. These data suggest that hyperglycemia alters [beta]-cell function through modification of the [K.sub.v] channel which may be associated with the RAS. renin-angiotensin system; electrophysiology; [K.sub.v]2.1 channel; losartan; PD123319; insulin secretion doi: 10.1152/ajpcell.00575.2008.

Am J Physiol Renal Physiol 298: F177-F186, 2010. First published October 28, 2009; doi:10.1152/ajprenal.00464.2009.--Angiotensin II (ANG II) stimulates proximal tubule (PT) sodium and water reabsorption. We showed that treating rats acutely with the angiotensin-converting enzyme inhibitor captopril decreases PT salt and water reabsorption and provokes rapid redistribution of the [Na.sup.+]/[H.sup.+] exchanger isoform 3 (NHE3), [Na.sup.+]/Pi cotransporter 2 (NaPi2), and associated proteins out of the microvilli. The aim of the present study was to determine whether acute ANG II infusion increases the abundance of PT NHE3, NaPi2, and associated proteins in the microvilli available for reabsorbing NaCl. Male Sprague-Dawley rats were infused with a dose of captopril (12 [micro]g/min for 20 min) that increased PT flow rate ~20% with no change in blood pressure (BP) or glomerular filtration rate (GFR). When ANG II (20 ng x [kg.sup.-1] x [min.sup.-1] for 20 min) was added to the captopril infusate, PT volume flow rate returned to baseline without changing BP or GFR. After captopril, NHE3 was localized to the base of the microvilli and NaPi2 to subapical cytoplasmic vesicles; after 20 min ANG II, both NHE3 and NaPi2 redistributed into the microvilli, assayed by confocal microscopy and density gradient fractionation. Additional PT proteins that redistributed into low-density microvilli-enriched membranes in response to ANG n included myosin VI, DPPIV, NHERF-1, ezrin, megalin, vacuolar [H.sup.+]-ATPase, aminopeptidase N, and clathrin. In summary, in response to 20 min ANG II in the absence of a change in BP or GFR, multiple proteins traffic into the PT brush-border microvilli where they likely contribute to the rapid increase in PT salt and water reabsorption. hypertension; captopril

Am J Physiol Renal Physiol 298: F125-F132, 2010. First published October 28, 2009; doi: 10.1152/ajprenal.00248.2009.--Glomerular endothelial cells (GEC) are strategically situated within the capillary loop and adjacent to the glomerular mesangium. GEC serve as targets of metabolic, biochemical, and hemodynamic signals that regulate the glomerular microcirculation. Unequivocally, hyperglycemia, hypertension, and the local renin-angiotensin system partake in the initiation and progression of diabetic nephropathy (DN). Whether free fatty acids (FFA) and reactive oxygen species (ROS) that have been associated with the endothelial dysfunction of diabetic macrovascular disease also contribute to DN is not known. Since endothelial cells from different organs and from different species may display different phenotypes, we employed human GEC to investigate the effect of high glucose (22.5 mmol/l), FFA (800 [micro]mol/l), and angiotensin II (ANG II; [10.sup.-7] mol/l) on the genesis of ROS and their effects on endothelial nitric oxide synthase (eNOS), cyclooxygenase-2 (COX-2), and the synthesis of prostaglandins (PGs). We demonstrated that high glucose but not high FFA increased the expression of a dysfunctional eNOS as well as increased ROS from NADPH oxidase (100%) and likely from uncoupled eNOS. ANG II also induced ROS from NADPH oxidase. High glucose and ANG II upregulated (100%) COX-2 via ROS and significantly increased the synthesis of prostacyclin ([PGI.sub.2]) by 300%. In contrast, FFA did not upregulate COX-2 but increased [PGI.sub.2] (500%). These novel studies are the first in human GEC that characterize the differential role of FFA, hyperglycemia, and ANG II on the genesis of ROS, COX-2, and PGs and their interplay in the early stages of hyperglcyemia. diabetes; prostaglandins; reactive oxygen species; nitric oxide

Am J Physiol Cell Physiol 298: C98-C106, 2010. First published October 21, 2009; doi: 10.1152/ajpcell.00321.2009.--As an endogenous physiologically active peptide, angiotensin (ANG) II plays an important role in the maintenance of blood pressure. In the arterial baroreceptor reflex (a pivotal regulator of blood pressure), aortic baroreceptor (AB) neurons located in the nodose ganglia (NG) are a primary afferent limb of the baroreflex. Hyperpolarization-activated currents ([I.sub.h]) in the AB neurons contribute to the excitability of the AB neurons. Therefore, the present study was to measure the modulating effect of ANG II on the [I.sub.h] in the primary AB neurons isolated from rats. Data from immunofluorescent and Western blot analyses showed that protein of [AT.sub.1] and [AT.sub.2] receptors was expressed in the nodose neurons. In the whole cell patch-clamp recording, ANG II concentration dependently enhanced the [I.sub.h] density in the AB neurons (100 nM ANG II-induced 53.8 [+ or -] 3.8% increase for A-type AB neurons and 30.4 [+ or -] 7.7% increase for C-type AB neurons at test pulse -140 mV, P < 0.05). ANG II also decreased membrane excitability in the AB neurons. [AT.sub.1] receptor antagonist (1 [micro]M losartan) but not [AT.sub.2] receptor antagonist (1 [micro]M PD-123,319) totally abolished the effect of ANG II on the [I.sub.h] and neuronal excitability. In addition, NADPH oxidase inhibitor (100 [micro]M apocynin) and superoxide scavenger (1 mM tempol) also significantly blunted the ANG II-induced increase of the [I.sub.h] and decrease of the membrane excitability in the AB neurons. Furthermore, losartan, apocynin, or tempol significantly attenuated the superoxide overproduction in the NG tissues induced by ANG II. These results suggest that ANG II-NADPH oxidase-superoxide signaling can activate the [I.sub.h] and subsequently decrease the membrane excitability of rat AB neurons. baroreflex; ion channels; NADPH oxidase; superoxide

Lutken SC, Kim SW, Jonassen T, Marples D, Knepper MA, Kwon TH, Frokiaer J, Nielsen S. Changes of renal AQP2, ENaC, and NHE3 in experimentally induced heart failure: response to angiotensin II [AT.sub.1] receptor blockade. Am J Physiol Renal Physiol 297: F1678-F1688, 2009. First published September 23, 2009; doi: 10.1152/ajprenal.00010.2009.--Heart failure (HF) was induced by ligation of the left anterior descending artery (LAD). Left ventricular end-diastolic pressure (LVEDP) >25 mmHg (at day 23 after LAD ligation) was the inclusion criterion. The rats were divided into three groups: sham-operated (Sham, n = 23, LVEDP: 5.6 [+ or -] 0.6 mmHg), HF (n = 14, LVEDP: 29.4 [+ or -] 1.4 mmHg), and candesartan (1 mg x [kg.sup.-1] [day.sup.-1] sc)-treated HI= (HF + Can, n = 9, LVEDP: 29.2 [+ or -] 1.2 mmHg). After 7 days (i.e., 29 days after LAD ligation) semiquantitative immunoblotting revealed increased abundance of inner medulla aquaporin-2 (AQP2) and AQP2 phosphorylated at [Ser.sup.256] (p-AQP2) in HF. There was also markedly enhanced apical targeting of AQP2 and p-AQP2 in inner medullary collecting duct (IMCD) in HF compared with Sham rats, shown by immunocyto-chemistry. Candesartan treatment significantly reversed the increases in both AQP2 and p-AQP2 expression and targeting. In contrast, there were only modest changes in other collecting duct segments. Semiquantitative immunoblots revealed increased expression of type 3 [Na.sup.+]/[H.sup.+] exchanger (NHE3) and [Na.sup.+]-[K.sup.+]-2[Cl.sup.-] cotransporter (NKCC2) in kidneys from HF compared with Sham rats: both effects were reversed or prevented by candesartan treatment. The protein abundance of [alpha]-epithelial sodium channel ([alpha]-ENaC) was increased while [beta]-ENaC and [gamma]-ENaC expression was decreased in the cortex and outer stripe of the outer medulla in HF compared with Sham rats, which was partially reversed by candesartan treatment. These findings strongly support an important role of angiotensin II in the pathophysiology of renal water and sodium retention associated with HF. collecting duct: aquaporin; type 3 [Na.sup.+]/[H.sup.+] exchanger; [Na.sup.+]-[K.sup.+]-2[Cl.sup.-] cotransporter; epithelial sodium channel doi: 10.1152/ajprenal.00010.2009

Bouley R, Palomino Z, Tang S-S, Nunes P, Kobori H, Lu HA, Shum WW, Sabolic I, Brown D, Ingelfinger JR, Jung FF. Angiotensin II and hypertonicity modulate proximal tubular aquaporin 1 expression. Am J Physiol Renal Physiol 297: F1575-F1586, 2009. First published September 23, 2009; doi: 10.1152/ajprenal.90762.2008.--Aquaporin 1 (AQP1) is the major water channel in the renal proximal tubule (PT) and thin descending limb of Henle, but its regulation remains elusive. Here, we investigated the effect of ANG II, a key mediator of body water homeostasis, on AQP1 expression in immortalized rat proximal tubule cells (IRPTC) and rat kidney. Real-time PCR on IRPTC exposed to ANG II for 12 h revealed a biphasic effect AQP1 mRNA increased dose dependently in response to [10.sup.-12] to [10.sup.-8] M ANG II but decreased by 50% with [10.sup.-7] M ANG II. The twofold increase of AQP1 mRNA in the presence of [10.sup.-8] M ANG II was abolished by the AT1 receptor blocker losartan. Hypertonicity due to either NaCl or mannitol also upregulated AQP1 mRNA by threeand twofold, respectively. Immunocytochemistry and Western blotting revealed a two- to threefold increase in AQP1 protein expression in IRPTC exposed concomitantly to ANG II ([10.sup.-8]M) and hypertonic medium (either NaCl or mannitol), indicating that these stimuli were not additive. Three-dimensional reconstruction of confocal images suggested that AQP1 expression was increased by ANG II in both the apical and basolateral poles of IRPTC. In vivo studies showed that short-term ANG II infusion had a diuretic effect, while this effect was attenuated after several days of ANG II infusion. After 10 days, we observed a twofold increase in AQPI expression in the PT and thin descending limb of Henle of ANG II-infused rats that was abolished when rats were treated with the selective [AT.sub.1]-receptor antagonist olmesartan. Thus ANG II increases AQP1 expression in vitro and in vivo via direct interaction with the [AT.sub.1] receptor, providing an important regulatory mechanism to link PT water reabsorption to body fluid homeostasis via the renin-angiotensin system. renin angiotensin system; proximal tubule doi: 10.1152/ajprenal.90762.2008

Only few studies have been devoted to the actions of the renin-angiotensin system (RAS) in the human gastrointestinal tract. The present study was undertaken to elucidate the expression and action of RAS in the human esophageal mucosa. Mucosal specimens with normal histological appearance were obtained from healthy subjects undergoing endoscopy and from patients undergoing esophagectomy due to neoplasm. Gene and protein expressions of angiotensin II (Ang II) receptor type 1 ([AT.sub.1]) and type 2 ([AT.sub.2]) and angiotensin-converting enzyme (ACE) were analyzed. In vivo functionality in healthy volunteers was reflected by assessing transmucosal potential difference (PD). Ussing chamber technique was used to analyze the different effects of Ang II on its [AT.sub.1] and [AT.sub.2] receptors. Immunoreactivity to [AT.sub.1] and [AT.sub.2] was localized to stratum superficiale and spinosum in the epithelium. ACE, [AT.sub.1], and [AT.sub.2] were found in blood vessel walls. Transmucosal PD in vivo increased following administration of the [AT.sub.1] receptor antagonist candesartan. In Ussing preparations mean basal transmural PD was -6.4 mV, epithelial current ([I.sub.ep]) 34 [micro]A/[cm.sup.2], and epithelial resistance ([R.sub.ep]) 321 [ohms] x [cm.sup.2]. Serosal exposure to Ang II increased PD as a result of increased [I.sub.ep], whereas [R.sub.ep] was constant. Ang II given together with the selective [AT.sub.1]-receptor antagonist losartan, or [AT.sub.2] agonist C21 given alone, resulted in a similar effect. Ang II given in presence of the [AT.sub.2]-receptor antagonist PD123319 did not influence PD, but [I.sub.ep] decreased and [R.sub.ep] increased. In conclusion, Ang II receptors and ACE are expressed in the human esophageal epithelium. The results suggest that [AT.sub.2]-receptor stimulation increases epithelial ion transport, whereas the [AT.sub.1] receptor inhibits ion transport and increases [R.sub.ep]. potential difference; epithelial current; epithelial resistance doi: 10.1152/ajpgi.00255.2009.

Angiotensin II induces RhoA activation through SHP2-dependent dephosphorylation of the RhoGAP p190A in vascular smooth muscle cells. Am J Physiol Cell Physiol 297: C1062-C1070, 2009. First published August 19, 2009; doi:10.1152/ajpcell.00174.2009.--Angiotensin II (ANG II) is a major regulator of blood pressure that essentially acts through activation of ANG II type 1 receptor (AT1R) of vascular smooth muscle cells (VSMC). AT1R activates numerous intracellular signaling pathways, including the small G protein RhoA known to control several VSMC functions. Nevertheless, the mechanisms leading to RhoA activation by AT1R are unknown. RhoA activation can result from activation of RhoA exchange factor and/or inhibition of Rho GTPase-activating protein (GAP). Here we hypothesize that a RhoGAP could participate to RhoA activation induced by ANG II in rat aortic VSMC. The knockdown of the RhoGAP p lg0A by small interfering RNA (siRNA) abolishes the activation of RhoA-Rho kinase pathway induced after 5 min of ANG II (0.1 [micro]M) stimulation in rat aortic VSMC. We then show that AT1R activation induces p190A dephosphorylation and inactivation. In addition, expression of catalytically inactive or phosphoresistant p190A mutants increases the basal activity of RhoA-Rho kinase pathway, whereas phosphomimetic mutant inhibits early RhoA activation by ANG II. Using siRNA and mutant overexpression, we then demonstrate that the tyrosine phosphatase SHP2 is necessary for 1) maintaining p190A basally phosphorylated and activated by the tyrosine kinase c-Abl, and 2) inducing p190A dephosphorylation and RhoA activation in response to AT1R activation. Our work then defines p190A as a new mediator of RhoA activation by ANG II in VSMC. p190A; phosphorylation; SH2-containing protein tyrosine phosphatase 2; Abelson tyrosine kinase doi: 10.1152/ajpcell.00174.2009.

Angiotensin II (ANG II) is taken up by proximal tubule (PT) cells via [AT.sub.1] ([AT.sub.1a]) receptor-mediated endocytosis, but the underlying cellular mechanisms remain poorly understood. The present study tested the hypothesis that the microtubule- rather than the clathrin-dependent endocytic pathway regulates [AT.sub.1]-mediated uptake of ANG II and ANG II-induced sodium and hydrogen exchanger-3 (NHE-3) expression in PT cells. The expression of [AT.sub.1] receptors, clathrin light (LC) and heavy chain (HC) proteins, and type 1 microtubule-associated proteins (MAPs; MAP-1A and MAP-1B) in PT cells were knocked down by their respective small interfering (si) RNAs before [AT.sub.1]-mediated FITC-ANG II uptake and ANG II-induced NHE-3 expression were studied. [AT.sub.1] siRNAs inhibited [AT.sub.1] expression and blocked ANG II-induced NHE-3 expression in PT cells, as expected (P < 0.01). Clathrin LC or HC siRNAs knocked down their respective proteins by ~90% with a peak response at 24 h, and blocked the clathrin-dependent uptake of Alexa Fluor 594-transferrin (P < 0.01). However, neither LC nor HC siRNAs inhibited [AT.sub.1]-mediated uptake of FITC-ANG II or affected ANG II-induced NHE-3 expression. MAP-1A or MAP-1B siRNAs markedly knocked down MAP-1A or MAP-1B proteins in a time-dependent manner with peak inhibitions at 48 h (>76.8%, P < 0.01). MAP protein knockdown resulted in ~52% decreases in [AT.sub.1]-mediated FITC-ANG II uptake and ~66% decreases in ANG II-induced NHE-3 expression (P < 0.01). These effects were associated with threefold decreases in ANG II-induced MAP kinases ERK 1/2 activation (P < 0.01), but not with altered [AT.sub.1] expression or clathrin-dependent transferrin uptake. Both losartan and [AT.sub.1a] receptor deletion in mouse PT cells completely abolished the effects of MAP-1A knockdown on ANG II-induced NHE-3 expression and activation of MAP kinases ERK1/2. Our findings suggest that the alternative microtubule-dependent endocytic pathway, rather than the canonical clathrin-dependent pathway, plays an important role in [AT.sub.1] ([AT.sub.1a])-mediated uptake of extracellular ANG II and ANG II-induced NHE-3 expression in PT cells. kidney; clathrin-coated pits; cytoskeleton; G protein-coupled receptor; MAP kinases; small interfering RNA doi: 10.1152/ajprenal.90734.2008.

To understand how rapid changes in blood pressure can regulate Na-K-ATPase in the kidney cortex, we tested the hypothesis that a short-term (5 min) decrease in renal perfusion pressure will increase the amount of Na-K-ATPase in the plasma membranes by an angiotensin II-dependent mechanism. The abdominal aorta of anesthetized Sprague-Dawley rats was constricted with a ligature between the renal arteries, and pressure was monitored on either side during acute constriction. Left renal perfusion pressure was reduced to 70 [+ or -] 1 mmHg (n = 6), whereas right renal perfusion pressure was 112 [+ or -] 4 mmHg. In control (nonconstricted) rats (n = 5), pressure to both kidneys was similar at 119 [+ or -] 6 mmHg. After 5 min of reduced perfusion, femoral venous samples were taken for plasma renin activity (PRA) and the kidneys excised. The cortex was dissected, minced, sieved, and biotinylated. Lower perfusion left kidneys showed a 41% increase (P < 0.003) in the amount of Na-K-ATPase in the plasma membrane compared with right kidneys. In controls, there was no difference in cell surface Na-K-ATPase between left and right kidneys (P = 0.47). PRA was 57% higher in experimental animals compared with controls. To test the role of angiotensin II in mediating the increase in Na-K-ATPase, we repeated the experiments (n = 6) in rats treated with ramiprilat. When angiotensin-converting enzyme was inhibited, the cell surface Na-K-ATPase of the two kidneys was equal (P = 0.46). These results confirm our hypothesis: rapid changes in blood pressure regulate trafficking of Na-K-ATPase in the kidney cortex. ouabain; sodium; blood pressure; renin doi: 10.1152/ajprenal.90363.2008.

To investigate the role of brain angiotensin II (ANG II) in the pathogenesis of injury following ischemic stroke, mice overexpressing renin and angiotensinogen (R + A +) and their wild-type control animals (R - A -) were used for experimental ischemia studies. Focal brain ischemia was induced by middle cerebral artery occlusion (MCAO). The severity of ischemic injury was determined by measuring neurological deficits and histological damage at 24 and 48 h after MCAO, respectively. To exclude the influence of blood pressure and local collateral blood flow, brain slices were used for oxygen and glucose deprivation (OGD) studies. The severity of OGD-induced damage was determined by measuring indicators of tissue swelling and cell death, the intensity of the intrinsic optical signal (IOS), and the number of propidium iodide (PI) staining cells, respectively. Results showed 1) R + A + mice showed higher neurological deficit score (3.8 [+ or -] 0.5 and 2.5 [+ or -] 0.3 for R + A + and R - A -, respectively, P < 0.01) and larger infarct volume (22.2 [+ or -] 1.6% and 14.1 [+ or -] 1.2% for R + A + and R - A -, respectively, P < 0.01); 2) The R + A + brain slices showed more severe tissue swelling and cell death in the cortex (IOS: 140 [+ or -] 6% and 114 [+ or -] 10%; PI: 139 [+ or -] 20 cells/field and 39 [+ or -] 9 cells/field for R + A + and R - A -, respectively, P < 0.01); 3) treatment with losartan (20 [micro]mol/1) abolished OGD-induced exaggeration of cell injury seen in R + A + mice. The data indicate that activation of ANG II/[AT.sub.1] signaling is harmful to brain exposed to ischemia. [AT.sub.1] receptor; mouse; losartan; middle cerebral artery doi: 10.1152/ajpregu.91040.2008.