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In addition to rapid responses comprising increases in blood pressure, drinking, and stimulation of natriuresis, ANG I1 induces the expression of transcription factors (TF) in the central nervous system. The ANG II metabolite ANG III (ANG 2–8) has been demonstrated to exert physiological effects similar to those of ANG II. We aimed to determine 1) whether ANG 1II induces TF expression in the brain, 2) which ANG II (AT) receptor subtype is involved, and 3) whether the two peptides, ANG II and ANG III, differ in their efficacy to stimulate TF expression. ANG II (100 pmol), ANG III (100 pmol), or vehicle was injected into the lateral brain ventricle of conscious rats alone or in combination with the AT1 receptor antagonist losartan (10 nmol), the AT2 receptor antagonist PD-123319 (5 nmol), or the aminopeptidase inhibitor amastatin (10 nmol). Similar to ANG II, ANG III induced the expression of c-Fos, c-Jun, and Krox-24 in four brain regions, subfornical organ, median preoptic area, paraventricular nucleus, and supraoptic nucleus of the hypothalamus, with the same efficacy. This effect was AT1 receptor mediated. Pretreatment with amastatin reduced the expression of TF in response to ANG II, indicating that this expression is partly mediated by ANG III. Interestingly, the AT2 receptor antagonist PD-123319 alone slightly enhanced the expression of c-Fos, c-Jun, and Krox-24 in different populations of neurons of the paraventricular nucleus. These data indicate that different populations of neurons in the paraventricular nucleus are tonically inhibited by AT2 receptors under physiological conditions. [ABSTRACT FROM AUTHOR]

The activity of the renin-angiotensin system (RAS) increases significantly in the late-gestation fetal sheep. Fetal cortisol is also increased during this time, and it is thought that the increase in cortisol may modulate the RAS changes. Previous studies have examined the effects of cortisol infusion on RAS activity, but the effects of blocking the peripartum increase in cortisol concentrations on the developmental changes in the RAS are not known. Therefore, we utilized the technique of hypothalamic-pituitary disconnection (HPD), which prevents the cortisol surge from occurring, to investigate the importance of the late-gestation increase in cortisol on the ontogenic changes in RAS activity. HPD of fetal sheep was performed at 120 days of gestational age (dGA), and fetuses were delivered between 135 and 139 dGA. Control fetuses were sham operated. HPD blocked the late-gestation cortisol increase but did not alter renal renin mRNA, renal renin or prorenin protein content, nor plasma renin levels compared with sham operated. However, HPD fetuses had increased ANG II receptor subtype 1 (AT1) mRNA and protein expression in the kidney and lungs. ANG II receptor subtype 2 (AT2) expression was not altered in these tissues at either mRNA or protein level. HPD did not change AT1 or AT2 mRNA in the left ventricle but did result in decreased protein levels for both receptors. These studies demonstrate that blockade of the naturally occurring increase in fetal cortisol concentration in late gestation is associated with tissue-specific alterations in expression of AT1 and AT2 receptors. These changes may impact on fetal tissue maturation and hence have consequences in postnatal life. [ABSTRACT FROM AUTHOR]

It is known that mice injected peripherally with ANG II do not show a drinking response but that cFos immunoreactivity (ir) is induced in brain regions similar to those in rats. We now show in Crl:CD 1(ICR) mice that peripheral injection of the ANG II type 1 receptor antagonist losartan was sufficient to prevent this induction of Fos-ir in the subfornical organ (SF0). Injection of ANG II into the lateral cerebral ventricle produced a robust water intake in mice and induced Fos-ir in SF0, as well as in median preoptic (MnPO) and paraventricular (PVN) nuclei. Peripheral injection of losartan blocked this drinking response and prevented the induction of Fos-ir in each of these brain regions. Hypovolemia produced by polyethylene glycol (PEG) produced a robust water intake but no evidence of sodium appetite, and it induced Fos-ir in SF0, MnPO, and PVN. Peripheral injection of losartan did not affect this drinking response. Fos-ir induced by PEG in SF0 and MnPO was reduced by treatment with losartan, while that induced in the PVN was further increased by losartan. Sodium depletion with furosemide and low-sodium diet produced a strong sodium appetite and induced Fos-ir in SF0 and MnPO. Treatment with losartan completely blocked the sodium appetite, as well as the induction of Fos-ir in these brain regions. These data indicate that endogenous production of ANG II and action at forebrain receptors is critically involved in depletion-related sodium appetite in mice. The absence of an effect of losartan on PEG-induced drinking suggests the critical involvement of other factor(s) such as arterial or venous baroreceptor input, and we discuss how this factor could also explain why peripheral ANG II is not dipsogenic in mice. [ABSTRACT FROM AUTHOR]

Boustany, Carine M., Kalyani Bharadwaj, Alan Daugherty, David R. Brown, David C. Randall, and Lisa A. Cassis. Activation of the systemic and adipose renin-angiotensin system in rats with diet-induced obesity and hypertension. Am J Physiol Regul Integr Comp Physiol 287: R943-R949, 2004. First published June 10, 2004; 10.1152/ajpregu.00265.2004.—In obesity-related hypertension, activation of the renin-angiotensin system (RAS) has been reported despite marked fluid volume expansion. Adipose tissue expresses components of the RAS and is markedly expanded in obesity. This study evaluated changes in components of the adipose and systemic RAS in diet-induced obese hypertensive rats. RAS was quantified in adipose tissue and compared with primary sources for the circulating RAS. Male Sprague-Dawley rats were fed either a low-fat (LF; 11% kcal as fat) or moderately high-fat (32% kcal as fat) diet for 11 wk. After 8 wk, rats fed the moderately high-fat diet segregated into obesity-prone (OP) and obesity-resistant (OR) groups based on their body weight gain (body weight: OR, 566 ± 10; OP, 702 ± 20 g; P < 0.05). Mean arterial blood pressure was increased in OP rats (LF: 97 ± 2; OR: 97 ± 2; OP: 105 ± 1 mmHg; P < 0.05). Quantification of mRNA expression by real-time PCR demonstrated a selective increase (2-fold) in angiotensinogen gene expression in retroperitoneal adipose tissue from OP vs. OR and LF rats. Similarly, plasma angiotensinogen concentration was increased in OP rats (LF: 390 ± 48; OR: 355 ± 24; OP: 530 ± 22 ng/ml; P < 0.05). In contrast, other components of the RAS were not altered in OP rats. Marked increases in the plasma concentrations of angiotensin peptides were observed in OP rats (angiotensin II: LF: 95 ± 31; OR: 59 ± 20; OP: 295 ± 118 pg/mi; P < 0.05). These results demonstrate increased activity of the adipose and systemic RAS in obesity-related hypertension. [ABSTRACT FROM AUTHOR]

Presents a study that tested the role of the sympathetic nervous system in the progressive increase in mean arterial pressure. Evidence for both an increase and a decrease in activity of the nitric oxide (NO) system in the diabetic state; Interrelationship between NO, the sympathetic nervous system and the renin-angiotensin system; Explanation for the increase in the blood pressure of rats.

Determines if there were any differences between the responses in chronically denervated kidneys compared with either intact or acutely denervated kidneys. Discussion on renal denervation; Examination of rabbits that have been made hypertensive using a continuous infusion of angiotensin II; Analysis of renal blood flow responses to phenylephrine.

Presents a study which determined the effects of angiotensin II receptor blockade on the response of the fetal right ventricle to pulmonary artery banding. Methods; Results; Discussion.

Presents a study which examined the implication of the renin-angiotensin system in regulation of splanchnic blood flow and glucose production in exercising humans. Methods; Results; Discussion.

Presents a study which determined how the different components of the renin-angiotensin-aldosterone axis respond to alterations in sodium intake in conscious mice. Methods; Results; Discussion.

Presents a study which compared the effects of angiotensin II on protein kinase C activity between young and adult rats. Methods; Results; Discussion.

Presents a study which investigated the role of circulating angiotensin II in sodium appetite after adrenalectomy. Methods; Results; Discussion.

Assesses the hypothesis that angiotensin (ANG) II-induced hypertension is enhanced during high salt intake through stimulation of endothelin (ET) type A receptors by endogenous ET-1. Increase in the mean arterial pressure with continuous intravenous infusion of ANG II; Comparison of the effect of ANG II in rats on high salt intake with rats on normal salt intake.

Features a study on the physiological and cellular responses to central application of angiotensin (ANG) II in ovine fetuses and the fetal central ANG-mediated dipsogenic sites in utero. Surgical preparation; Behavioral and physiological experiments; Data analysis.

Presents a study which determined if glucocorticoids potentiate central hypertensive actions of angiotensin II to increase arterial pressure in rats. Role of glucocorticoids in the pathogenesis of essential hypertension; Methods used; Results; Discussion.

Presents a study which determined whether activation of the renin-angiotensin system within the nucleus of the solitary tract plays a role in enhanced sympathetic nerve activity in heart failure (HF). Characteristics of chronic HF; Effect of angiotensin-converting enzyme inhibitors on chronic HF; Methods used; Results.

Presents information on a study which examined the role of endothelin in mediating the renal hemodynamic and arterial pressure changes during chronic angiotensin II-induced hypertension. Methodology; Results of the study; Discussion.

Focuses on a study which evaluated angiotensin messenger RNA expression in the midcaudal arcuate nucleus of the rat brain during lactation. Methods; Results; Discussion.

Focuses on a study which evaluated whether the antiangiogenic effect of angiotensin-(1-7) in the mouse sponge model of angiogenesis might be receptor mediated and involved in the release of nitric oxide. Materials and methods; Results; Discussion.

Presents information on a study which examined the effects of blockade of the renin-angiotensin system on the renal metabolism of arachidonic acid in rats. Methods used; Results; Discussion.

Presents information on a study which examined the effect of oral contraceptive usage on the renin angiotensin system in healthy, premenopausal women. Background on oral contraceptive medications; Methods used in the study; Results; Discussion.

Focuses on a study which discussed TGR(ASrAOGEN)680, a transgenic rat line which exhibits decreased brain angiotensinogen content associated with a mild diabetes insipidus and lower blood pressure. Materials and methods of the study; Results; Discussion of the results.

Focuses on a study which conducted experiments on how a lesion of the subfornical organ may reduce sodium depletion-induced salt appetite, which is largely dependent on angiotensin II. Methodology; Results of the study; Discussion of the results.

Focuses on a study which examined the activity and responsiveness of the renin-angiotensin system in the aging rat. Methods; Details on studies of chronic angiotensin-converting enzyme inhibitors; Assessment of the functional conversion of angiotensin (ANG) I to ANG II.

Presents information on a study which investigated whether angiotensin II is involved in the enhancement seen in dehydrated rats of the fever induced by bacterial endotoxin. Methods used in the study; Results and discussion.

Presents information on a study which examined the renal and cardiovascular responses to an intravenous infusion of angiotensin II in ovine fetuses at midgestation. Methods used in the study; Results and discussion.

Presents information on a study which evaluated the role of endogenous renin-angiotensin system in copius drinking of seawater eels. Methodology; Effects of SQ-14225 and an anti-ANG II serum on drinking, plasma ANG II hormone, and blood pressure; Role of ANG II hormone in drinking of seawater fish.

Focuses on a study which discussed the low lower body negative pressure tolerance in men associated with attenuation of the renin-angiotensin system. Information on the mechanisms for reduction of cerebral blood pressure; Methodology; Results of the study.

Presents information on a study which investigated whether intrarenal angiotensin II in anesthetized rabbits acts preferentially on pre- or postglomerular vessels. Background of the capability of angiotensin II; Methodology used; Results and its implications.

Features a study on the role of central angiotensinergic and chlorinergic mechanisms in octreotide-induced drinking, blood pressure and vasopressin secretion in the rat. Methodology of the study; Results and discussion; Conclusion.

Presents information on a study which investigated the existence of an intrarenal renin-angiotensin system in rainbow trout. Materials and methods; Results and discussion.

Focuses on a study which explored the mechanisms for the stimulation of respiration by angiotensin II receptor using spontaneously hypertensive rats. Methodology of the study; Results of the study; Discussion and conclusion.

Reveals a study that compared systemic and local intra-arterial angiotensin II (ANG II) infusions in near-term pregnant and ovariectomized nonpregnant ewes to determine how ANG II increases uterine vascular resistance. Methodology; Basal hemodynamic data; Comparison of systemic and local ANG II infusions in nonpregnant ewes; Discussion.

Provides information on a study which explored the role of angiotensin (ANG)-converting enzyme (ACE) and ANG II in amphibian testicular steroidogenesis and prostaglandin production. Materials and methods of the study; Results; Discussion of the results.

Presents information on a study which examined the receptors for angiotensin II in the rat brain during lactation and diestrus of the estrous cycle. Methodology of the study; Results and discussion; Conclusion.

Focuses on a study on the role and mechanism of angiotensin II in the sensitization of arterial blood pressure (ABP) to dietary salt in atrial natriuretic peptide (ANP) knockout mice. Methodology of the study; Results and discussion; Conclusion.

Presents a study which investigated the roles of increased bradykinin and decreased angiotensin II action on insulin-stimulated glucose transport activity in obese Zucker rat. Methods used; Results; Conclusion.

Presents a study which examined the role of nitric oxide (NO) in the control of systemic hemodynamic response. Role of angiotensin (ANG) in modulating the systemic hemodynamic response in NO synthesis blockade; Participation of ANG II in the L-nitro arginine methyl ester (NAME)-induced increase in microvascular permeability.

Investigates whether angiotensin (ANG) I alters the electrical activity of rat subfornical organ (SFO) neurons and compares the effect with the same neurons on ANG II. Effects of ANG I and II on the neurons of the SFO; Assessment on the excitatory response after superfusion with ANG I; Drinking pattern and response times after drug treatments.

Presents a study which examined the temporal maturation of sodium appetite after furosemide treatment and the associated changes in plasma levels of angiotensin (ANG) II and aldosterone and plasma volume in rats. Methodology of the study; Results and discussion; Conclusion.

Presents information on a study which examined the role of prostaglandins and angiotensin in the renal vasodilatation caused by cortisol in conscious sheep. Effect of intrarenal indomethacin on the renal hemodynamic response to intravenous cortisol; Effect of intravenous captopril; Discussion of results.

Presents information on a study that tested whether common bile duct (BDL) rats have hypotension during sodium depletion or an elevated dipsogenic response to angiotensin II (ANG II) that might help to explain the saline intake. How the study was conducted; Verification on the effectiveness of ligation; Discussion of the dose-response experiment; Statistical analysis.

Presents a study investigating the effect of intracerebroventricular administration of the angiotensin receptor antagonist losartan on the natriuresis, pressor effect, and arginine vasopressin secretion. Effect of centrally administered losartan; Materials and methods used in the study; What the results suggest.

Presents a study that determines the role of angiotensin subtype 1 and 2 receptors. Mechanisms by which these receptors act to alter fluid transport in a rat jejunum; Methodology used in the study; Effects of sodium restriction on jejunal water transport; Effect of guanethidine and prazosin on jejunal fluid transport.

Presents information on a study that tested the hypothesis that angiotensin II (ANG II) contributes to the ventilatory and acid-base adaptations during hypoxia. Methodology used in the study; Effects of ANG II receptor block on gas exchange and metabolism during hypoxia; Response to Dejours oxygen test; What the results indicate.

Presents information on a study that tested the effect of angiotensin II infusion in vivo on basal cortisol concentrations and fetal adrenal responsiveness to an adreno corticotropic hormone challenge. Methodology used in the study; Activation of the fetal hypothalamo-pituitary-adrenal axis; What the results indicate.

Presents information on a study that tests the hypothesis that the area postrema is necessary for endogenous angiotensin II (ANG II) to chronically maintain lumbar sympathetic nerve activity (LSNA) and heart rate in conscious sodium-deprived rats. Effect of the NAG II type 1-receptor antagonist, losartan on LSNA; What the results suggest.

Presents information on a study that examines the regulation of the angiotensinogen gene in cardiac myocytes in response to angiotensin II (ANG II) and stretch. What the results indicate; Factors involved in stretch-mediated activation of the angiotensinogen in cardiac myocytes.

Investigates the effect of interactions between nitric oxide (NO) and angiotensin II on pressure diuresis and natriuresis. Effects of Nw-nitro-L-arginine methyl ester on renal function; Influence of angiotensin receptor blockade on arterial pressure and renal function; Interactions between angiotensin II and NO on pressure diuresis.

Tests the hypothesis that endogenous angiotensin II and angotensin type 1 (AT1) receptors participate in the development of fetal right ventricular hypertrophy. Effects of pulmonary artery (PA) banding and losartan on fetal hemodynamics and arterial blood values; Influence of PA banding and AT1 receptor blockade on fetal somatic and cardiac mass.

Investigates the effect of norepinephrine (NE) on the expression of the type 1 angiotensin II (ANG II) receptor (AT1) in the aorta and vascular smooth muscle cells of rats. Interactions between the renin-angiotensin system and the sympathetic nervous system; Possible mechanisms by which NE induces downregulation of the AT1 receptor in the vascular tissue.