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Salt sensitive hypertension is associated with variants of G protein-coupled receptor kinase 4γ (GRK4), as well as with activating variants of the solute carrier family 4 member 5 (rs7571842 and rs10177833; SLC4a5), which encodes the sodium bicarbonate transporter 2 (NBCe2). We tested the hypothesis that the effect of the R65L variant (rs2960306) of GRK4 (GRK4γ 65L) on salt-sensitivity involves a gene-gene interaction with SLC4a5 variants. We found that the renal expression of SLC4a5 is increased in salt sensitive transgenic mice expressing GRK4γ 65L and is higher (50%; n=4; P<0.02) than that in GRK4 γ expressing the wild type variant (WT). Moreover, that AAV9-mediated renal specific overexpression of SLC4a5 in GRK4γ 65L mice increases the blood pressure (BP) response to a high salt diet compared with mice expressing empty vector (n=3; P<0.05). We studied human renal proximal tubule cells (hRPTCs) endogenously expressing GRK4 WT and SLC4a5 WT, GRK4 65L, SLC4a5 variants and both GRK4 65L and SLC4a5 variants. SLC4A5 expression is increased in hRPTCs expressing GRK4 65L and in cells expressing both GRK4 65L and SLC4a5 variants (n=5, P<0.05) compared with GRK4 WT. GRK4 can interact with nuclear histone deacetylases (HDACs) and co-immunoprecipitates with HDAC1 in nuclear fractions of hRPTCs. Renal-selective downregulation of HDAC1 increases BP in C57Bl/6J (P<0.05) mice. hRPTCs carrying both GRK4 65L and SLC4a5 variants have decreased expression (60%; n=4; P<0.05) of HDAC1 compared with cells expressing GRK4 WT and SLC4a5 WT or GRK4 65L This correlates with increased histone H4 acetylation but unchanged H2A, H2B and H3 acetylation in cells carrying both variants. Our results indicate a complex interaction between these variants in the regulation not only of SLC4a5 expression but that of other genes involved in salt sensitivity.

Lack or downregulation of the dopamine D2receptor (D2R) results in increased renal expression of injury markers and proinflammatory factors that is independent of a blood pressure increase. This study aimed to determine the mechanisms involved in the regulation of renal inflammation by D2Rs. Silencing D2Rs in mouse renal proximal tubule cells increased the expression of the proinflammatory TNF-α, monocyte chemoattractant protein-1 (MCP-1), and IL-6. D2R downregulation also increased Akt phosphorylation and activity, and glycogen synthase kinase-3β (GSK3β) phosphorylation and cyclin D1 expression, downstream targets of Akt; however. phosphatidylinositol 3-kinase (PI3K) activity was not affected. Conversely, D2R stimulation decreased Akt and GSK3β phosphorylation and cyclin D1 expression. Increased phospho-Akt, in the absence of increased PI3K activity, may result from decreased Akt dephosphorylation. Inhibition of protein phosphatase 2A (PP2A) with okadaic acid reproduced the effects of D2R downregulation on Akt, GSK3β, and cyclin D1. The PP2A catalytic subunit and regulatory subunit PPP2R2C coimmunoprecipitated with the D2R. Basal phosphatase activity and the expression of PPP2R2C were decreased by D2R silencing that also blunted the increase in phosphatase activity induced by D2R stimulation. Similarly, silencing PPP2R2C also increased the phosphorylation of Akt and GSK3β. Moreover, downregulation of PPP2R2C resulted in increased expression of TNF-α, MCP-1, and IL-6, indicating that decreased phosphatase activity may be responsible for the D2R effect on inflammatory factors. Indeed, the increase in NF-κB reporter activity induced by D2R silencing was blunted by increasing PP2A activity with protamine. Our results show that D2R controls renal inflammation, at least in part, by modulation of the Akt pathway through effects on PP2A activity/expression.

Sorting nexin 5 (SNX5) belongs to the SNX family, which is composed of a diverse group of proteins that mediate trafficking of plasma membrane proteins, receptors, and transporters. SNX5 is important in the resensitization of the dopamine D1-like receptor (D1R). D1R is uncoupled from its effector proteins in hypertension and diabetes, and treatment of diabetes restores D1R function and insulin receptor (IR) expression. We tested the hypothesis that the D1R and SNX5 regulate IR by studying the expression, distribution, dynamics, and functional consequences of their interaction in human renal proximal tubule cells (hRPTCs). D1R, SNX5, and IR were expressed and colocalized in the brush border of RPTs. Insulin promoted the colocalization of SNX5 and IR at the perinuclear area of hRPTCs. Unlike SNX5, the D1R colocalized and coimmunoprecipitated with IR, and this interaction was enhanced by insulin. To evaluate the role of SNX5 and D1R on IR signaling, we silenced via RNA interference the endogenous expression of SNX5or the D1R gene DRD1in hRPTCs. We observed a decrease in IR expression and abundance of phosphorylated IR substrate and phosphorylated protein kinase B, which are crucial components of the IR signal transduction pathway. Our data indicate that SNX5 and D1R are necessary for normal IR expression and activity. It is conceivable that D1R and SNX5 may interact to increase the sensitivity to insulin via a positive regulation of IR and insulin signaling.

Salt sensitivity is estimated to be present in 51% of the hypertensive and 26% of the normotensive populations. The individual blood pressure response to salt is heterogeneous and possibly related to inherited susceptibility. Although the mechanisms underlying salt sensitivity are complex and not well understood, genetics can help to determine the blood response to salt intake. So far only a few genes have been found to be associated with salt-sensitive hypertension using candidate gene association studies. The kidney is critical to overall fluid and electrolyte balance and long-term regulation of blood pressure. Thus, the pathogenesis of salt sensitivity must involve a derangement in renal NaCl handling: an inability to decrease renal sodium transport and increase sodium excretion in the face of an increase in NaCl load that could be caused by aberrant counter-regulatory natriuretic/antinatriuretic pathways. We review here the literature regarding the gene variants associated with salt-sensitive hypertension and how the presence of these gene variants influences the response to antihypertensive therapy.

The homeostatic control of blood pressure hinges upon the delicate balance between prohypertensinogenic and antihypertensinogenic systems. D1-like dopamine receptors [dopamine D1and D5receptors (D1Rs and D5Rs, respectively)] and the α1A-adrenergic receptor (α1A-AR) are expressed in the renal proximal tubule and engender opposing effects on Na+transport, i.e., natriuresis (via D1Rs and D5Rs) or antinatriuresis (via α1A-ARs). We tested the hypothesis that the D1R/D5R regulates the α1A-AR. D1-like dopamine receptors coimmunoprecipitated, colocalized, and cofractionated with α1A-ARs in lipid rafts in immortalized human renal proximal tubule cells. Long-term treatment with the D1R/D5R agonist fenoldopam resulted in decreased D1R and D5R expression but increased α1A-AR abundance in the plasma membrane. Short-term fenoldopam treatment stimulated the translocation of Na+-K+-ATPase from the plasma membrane to the cytosol that was partially reversed by an α1A-AR agonist, which by itself induced Na+-K+-ATPase translocation from the cytosol to the plasma membrane. The α1A-AR-specific agonist A610603 also minimized the ability of fenoldopam to inhibit Na+-K+-ATPase activity. To determine the interaction among D1Rs, D5Rs, and α1A-ARs in vivo, we used phenylephrine and A610603to decrease Na+excretion in several D1-like dopamine receptor knockout mouse strains. Phenylephrine and A61603treatment resulted in a partial reduction of urinary Na+excretion in wild-type mice and its abolition in D1R knockout, D5R knockout, and D1R-D5R double-knockout mice. Our results demonstrate the ability of the D1-like dopamine receptors to regulate the expression and activity of α1A-AR. Elucidating the intricacies of the interaction among these receptors is crucial for a better understanding of the crosstalk between anti- and pro-hypertensive systems.

Dopamine is an important regulator of systemic blood pressure via multiple mechanisms. It affects fluid and electrolyte balance by its actions on renal hemodynamics and epithelial ion and water transport and by regulation of hormones and humoral agents. The kidney synthesizes dopamine from circulating or filtered l-DOPA independently from innervation. The major determinants of the renal tubular synthesis/release of dopamine are probably sodium intake and intracellular sodium. Dopamine exerts its actions via two families of cell surface receptors, D1-like receptors comprising D1R and D5R, and D2-like receptors comprising D2R, D3R, and D4R, and by interactions with other G protein-coupled receptors. D1-like receptors are linked to vasodilation, while the effect of D2-like receptors on the vasculature is variable and probably dependent upon the state of nerve activity. Dopamine secreted into the tubular lumen acts mainly via D1-like receptors in an autocrine/paracrine manner to regulate ion transport in the proximal and distal nephron. These effects are mediated mainly by tubular mechanisms and augmented by hemodynamic mechanisms. The natriuretic effect of D1-like receptors is caused by inhibition of ion transport in the apical and basolateral membranes. D2-like receptors participate in the inhibition of ion transport during conditions of euvolemia and moderate volume expansion. Dopamine also controls ion transport and blood pressure by regulating the production of reactive oxygen species and the inflammatory response. Essential hypertension is associated with abnormalities in dopamine production, receptor number, and/or posttranslational modification. © 2011 American Physiological Society. Compr Physiol1:1075-1117, 2011.

Renal proximal tubular sodium reabsorption is regulated by sodium transporters, including the sodium glucose transporter, sodium amino acid transporter, sodium hydrogen exchanger isoform 3 and sodium phosphate cotransporter type 2 located at the luminal/apical membrane, and sodium bicarbonate cotransporter and Na/KATPase located at the basolateral membrane. This review summarizes recent studies on sodium transporters that play a major role in the increase in blood pressure in essential/polygenic hypertension.

Angiotensin II was initially described as a hormone of peripheral origin, the active end product of the Renin-Angiotensin System. The subsequent discovery that Angiotensin II was locally formed and selectively regulated in most organs indicated that tissue Angiotensin II systems might play additional important roles. After initial controversy, the presence of an Angiotensin II system in the brain is now universally accepted. Brain Angiotensin II is probably involved in the regulation of many brain functions. Angiotensin II AT1 receptors are localized not only in areas related to the regulation of autonomic and endocrine control, but also in many other areas of the brain involved in emotional, sensory and motor functions. Angiotensin II AT2 receptors are more abundant in brain areas related to sensory and motor control. The roles of brain Angiotensin II appear to be multiple and complex. In addition to a regulatory role in the control of the autonomic and hormone systems, the peptide participates in brain development, sensory processes, cognition and in the regulation of cerebrovascular flow. Recent developments indicate that blockade of the brain Angiotensin II AT1 receptors not only contributes to a significant blood pressure decrease in hypertension, but that simultaneous antagonism of peripheral and brain AT1 receptors reduces the sympathoadrenal and hormonal responses to stress and prevents stress-induced gastric injury. A novel role emerges for the use of peripheral and centrally acting AT1 receptor antagonists as therapeutically advantageous for the treatment of stress-related disorders.

AT2receptors may act in opposition to and in balance with AT1receptors, their stimulation having beneficial effects. We found renal AT2receptor expression in female mice higher than in male mice. We asked the question of whether such expression might be estrogen dependent. In male, female, ovariectomized, and estrogen-treated ovariectomized mice, we studied renal AT1and AT2receptors by immunocytochemistry and autoradiography, AT2receptor mRNA by RT-PCR, and cAMP, cGMP, and PGE2by RIA. AT1receptors predominated. AT2receptors were present in glomeruli, medullary rays, and inner medulla, and in female kidney capsule. AT1and AT2receptors colocalized in glomeruli. Female mice expressed fewer glomerular AT1receptors. Ovariectomy decreased AT1receptors in medullary rays and capsular AT2receptors. Estrogen administration normalized AT1receptors in medullary rays and increased AT2receptors predominantly in capsule and inner medulla, and also in glomeruli, medullary rays, and inner stripe of outer medulla. In medullas of estrogen-treated ovariectomized mice there was higher AT2receptor mRNA, decreased cGMP, and increased PGE2content. We propose that the protective effects of estrogen may be partially mediated through enhancement of AT2receptor stimulation.

Abstract: This study determined the effects of thyroid hormone on the renal dopaminergic system. Surgical thyroidectomy (Tx) and treatment with 2-thiouracil (Thio) decreased renal cortex Na+/K+ ATPase activity and urinary volume. Tx also decreased urinary Na+ and urinary l-DOPA without changing urinary excretion of Dopamine (DA). Thio treatment decreased slightly urinary l-DOPA and Na+, but increased urinary excretion of DA. In both models of thyroid hormone deficiency, the ratio urinary DA/DOPA increased. Changes after Thio treatment were reversed after one month of drug withdrawal. Treatment with T3 via osmotic minipump increased Na+/K+ ATPase activity and urinary l-DOPA, did not change urinary DA, and increased the ratio DA/DOPA. To further analyze the effects of thyroid hormone deficiency, we administered selective DA1 (SCH-23390), DA2 (Sulpiride), and a non selective (Haloperidol) DA receptor antagonists to Thio treated and control animals. The DA1 antagonist decreased diuresis, natriuresis and urinary l-DOPA in control, but had no effect in Thio treated rats. Sulpiride had no effect in either group. The combination of SCH-23390 plus Sulpiride decreased urinary l-DOPA and urinary volume only in Thio treated animals. Haloperidol decreased urinary volume in Thio treated animals, but had no effect in controls. Our findings suggest that renal DA synthesis is to some extent dependent on thyroid hormone levels, and that the response of DA receptors is altered by thyroid hormone deficiency, indicating a role of this hormone in the regulation of the renal dopaminergic system.

Background/Aims:This study determined alterations in renal dopamine production in streptozotocin-treated rats and explored the mechanisms underlying this alteration. Methods:Streptozotocin (65 mg/kg) or vehicle was administered to 3-month-old male Wistar rats. Treated animals had hyperglycemia, glycosuria and increased diuresis, natriuresis and excretion of L-dopa. Urinary dopamine and dihydroxyphenylacetic acid were similar to those in control animals. The production of dopamine by renal cortex slices from treated rats was significantly less than that from control animals. The addition of glucose (8.4–18.4 mM) to the incubation medium decreased about 40% the uptake of L-dopa by isolated proximal tubular cells. Scatchard analysis of the saturation curves obtained in this condition showed a decrease in the Vmax without changes in the Km. Results:Our results confirm previous studies suggesting a renal dopaminergic deficiency in insulin-dependent diabetes and provide evidence strongly suggesting that a decrease in the number of tubular L-dopa transport sites is the underlying defect of this deficiency. Conclusion:These results highlight the role of the uptake of dopa as an important modulator of renal dopamine synthesis.

This study assessed the role of adrenergic receptors on the regulation of the uptake of l-dopa and the production of dopamine by renal tubular cells. Scatchard analysis showed two l-dopa uptake sites with different affinities (Km0.316 vs 1.53 μM). l-Dopa uptake was decreased by the nonselective adrenergic agonists epinephrine or norepinephrine (40%), by the β-selective agonist isoproterenol or the β2-selective agonist terbutaline (60%), but not by α-selective agonists (all 1 μM). The effect of norepinephrine, isoproterenol, or terbutaline was unaffected by addition of the β1-antagonist atenolol, abolished by ICI-118,551, a β2-antagonist (both 0.1 μM), and mimicked by the addition of dibutyryl-cAMP (1 μM). Preincubation with terbutaline decreased the number of high-affinity uptake sites (Vmax= 1.10 ± 0.3 vs. 0.5 ± 0.1 pmol · mg protein−1· min−1) without changing their affinity. Norepinephrine or terbutaline decreased dopamine production by isolated cells, and this effect was abolished by ICI-118,551 (0.1 μM). In vivo administration of ICI-118,551 reduced the urinary excretion of l-dopa and increased the excretion of 3,4-dihydroxyphenylacetic acid without significant changes in plasma l-dopa concentrations. These results demonstrate that stimulation of β2-adrenergic receptors decreases the number of high-affinity l-dopa uptake sites in isolated tubular cells resulting in a reduction of the uptake of l-dopa and the production of dopamine and provide evidence for the presence of this mechanism in the intact animal.

Norepinephrine is a major regulator of the release of growth hormone. Diethyldithiocarbamate, a dopamine-β-hydroxylase inhibitor, reduces norepinephrine synthesis and acutely inhibits growth hormone (GH) secretion. To investigate the long-term effects of dopamine-β-hydroxylase blockade on growth, we administered diethyldithiocarbamate (0, 40, 100 or 400 mg/kg sc b.i.d.) to 21-day-old female rats for 10 days. Food intake, body weight, and tail length were measured twice a week. Plasma GH levels and hypothalamic dopamine and norepinephrine content were measured; messenger ribonucleic acids (mRNAs) for GH-releasing hormone and somatostatin were determined by quantitative in situ hybridization. Diethyldithiocarbamate administration decreased GH levels (p<0.05) and retarded growth in a dose-dependent manner (p<0.05), without altering food intake. Co-administration of GH partially reversed the growth retardation in diethyldithiocarbamate-treated animals (p<0.05). Diethyldithiocarbamate treatment also increased the hypothalamic dopamine/norepinephrine ratio (1.13 vs 0.41 control, p<0.05). Local levels of GH-releasing hormone and somatostatin mRNA were not altered by treatment. After discontinuation of diethyldithiocarbamate, growth rates returned to normal or transiently even to supranormal values. Norepinephrine synthesis blockade with diethyldithiocarbamate provides a model for reversible growth retardation, in which GH levels are decreased in the absence of decreased GH-releasing hormone mRNA. These results support a role for norepinephrine in the regulation of normal growth.

Objectives. This study evaluated the safety, efficacy and validity of 6-[18F]fluorodopamine positron emission tomographic scanning of cardiac sympathetic innervation and function in humans.

Summary Contrary to prediction, loading rats with tryptamine, tryptophan or methanol failed to produce any rise in endogenous monoamine oxidase inhibitor output, whilst ethanol administration resulted in a significantly decreased excretion. These findings, which provide no support for the hypothesis that the inhibitor is aß-carboline, may shed some light on the tranquillizing effect of ethanol in man.

Summary The inhibitory action of a range ofβ-carbolines on human and rat monoamine oxidase (MAO) A and B has been studied. Concentrations of 5-hydroxytryptamine and phenylethylamine, approximately at their Km values, were used as substrates for MAO A and B respectively. A wide variation in selectivity was found, with harmaline being 10,000 times more potent an inhibitor of A than B whereas, using tetrahydro-β-carboline and harmane, the difference was nearer to ten-fold. Of the carbolines which have been found endogenously, tetrahydro-β-carboline, 6-methoxytetrahydro-β-carboline and harmane are all sufficiently potent inhibitors of human MAO A, with I50 values of 5×10−6, 10−6, 5×10−7M respectively, for this property to be of possible physiological significance. Harmane, with an I50 of 5×10−6M, might also play a role as an inhibitor of MAO B.

1. To determine the sources of dopa (3,4-dihydroxyphenylalanine) in plasma, we measured regional arteriovenous differences, tissue concentrations and urinary excretion of dopa during systemic intravenous infusions of I-[3H]dopa into anaesthetized intact rats and rats pretreated with the sympathetic neurotoxin, 6-hydroxydopamine. 2. In intact rats, large arteriovenous increments in plasma dopa concentrations were noted in the femoral (47%) and adrenal (141%) beds, with a small arterial-portal venous increment (11%), whereas in the kidney there was a substantial (47%) arteriovenous decrement in plasma dopa levels. Skeletal muscle appeared to be a major source of dopa in arterial plasma. 3. Treatment with 6-hydroxydopamine abolished the afferent-efferent increment of plasma dopa concentrations in the femoral bed. The arteriovenous decrement of plasma dopa concentrations in the kidney was preserved, and the arteriovenous increment in the adrenal bed was decreased by about half. Arterial plasma dopa levels fell by 41%. 4. Regional extraction percentages of I-[3H]dopa were used to estimate the clearances and rates of appearance (spillovers) of dopa in plasma. Dopa spillover was detected in the femoral, renal, splanchnic and adrenal beds, with skeletal muscle accounting for about 44% and the kidneys accounting for about 18% of dopa in arterial plasma. Whereas chemical sympathectomy decreased the femoral and renal spillover of dopa by 90% or more, arterial dopa levels and estimated dopa spillover into arterial plasma were decreased by only about 45%. 5. The kidneys accounted for 22% of dopa clearance from arterial plasma. From the renal extraction of I-[3H]dopa and the urinary excretion of [3H]dopamine, it was estimated that 77% of dopa removed in the kidneys was excreted as dopamine in intact animals and 69% was excreted as dopamine in sympathectomized animals. Conversely, about 80% of urinary endogenous dopamine was derived from plasma dopa, regardless of 6-hydroxydopamine treatment. 6. The results indicate that endogenous dopa in arterial plasma is derived substantially but not exclusively from sympathetic nerve endings that are destroyed by 6-hydroxydopamine, especially in skeletal muscle and the kidneys. Regional dopa spillover therefore probably reflects regional catecholamine biosynthesis. In rats, urinary dopamine is derived mainly from renal decarboxylation of circulating dopa.

1.The effect of benzodiazepine pretreatment on the stress-induced decrease in MAO activity in rat tissues using footshock as stress model was investigated.2.Animals were injected with vehicle, Lorazepam (1.25 mg/kg), or Clonazepam (0.5 mg/kg) 2 hr before or with PK 11195 (0.45 mg/kg) 2.5 hr before being subjected to one session of 10 inescapable footshocks or to a sham session. At the end of the session animals were sacrificed and MAO A and B activities in hearts and brains were determined.3.Pretreatment of the animals with both Lorazepam and Clonazepam abolished the decrease induced by footshock in MAO A activity in brain. Pretreatment with Lorazepam but not with Clonazepam abolished the stressinduced decrease in MAO A in the heart. Pretreatment with PK 11195 before Lorazepam reversed its effects in the heart but not in the brain. Neither footshock nor any of the drugs used had any effect on heart and brain MAO B.4.Our results suggest that in the heart but not in the brain, peripheral benzodiazepine receptors play a role in the regulation of MAO A activity under stress conditions.

1.The effect of repeated isolation stress on MAO inhibitory activity (tribulin) in rat tissues as well as on plasma catecholamine levels was invstigated.2.Animals were subjected to a daily period of isolation (9min) and sacrificed on days 1, 2, 4, and 5.3.In brain and cerebellum the levels of both inhibitory activities were found to be significantly higher in animals sacrificed on days 1–2 than in either controls or animals sacrificed on days 4–5.4.In heart and kidney the highest levels of both activities were found in animals sacrificed on days 4–5.5.Plasma levels of dopamine on day 4 were significantly higher than those in controls or in any of the experimental groups. Plasma levels of epinephrine showed step-by-step increments from day 1 up to day 5, reaching statistical significance only on day 5. Plasma levels of norepinephrine were significantly increased on days 2, 4, and 5.6.Under the experimental conditions of this study, we have shown a rapid and short-lasting increment of tribulin in the central nervous system. Its disappearance on days 4–5 could be related to adaptation to the novel situation. Changes in the peripheral tissues appeared later, and a similar adaptation was absent during the period of observation.7.Tribulin would be related to the stressful situation not only as an anxiety-promoting agent but also in contributing to the maintenance of high levels of circulating catecholamines.

Previous studies from our laboratory show that in mice increased expression/function of the orphan receptor GPR83 is associated with salt resistance. GPR83 is expressed in proximal and distal convoluted tubules in mouse kidney. Global deletion or renal specific silencing of the GPR83 gene increases systolic blood pressure (SBP) and is associated with increased GRK4 expression in the kidney. Recent evidence indicated that peptides derived from the Proprotein Convertase Subtilisin/Kexin Type 1 Inhibitor (PCSK1N) may be the endogenous ligands of GPR83. We hypothesized that these peptides are implicated in the regulation of blood pressure. Renal specific siRNA mediated silencing of PCSK1N in mice resulted in an increase in SBP (130?4 vs control 100?1 mmHg, n=3/group; P<0.05); this was associated with decreased Na+ excretion (P<0.05) and with decreased renal GPR83 and increased GRK4 expressions. Renal restricted infusion of PCSK1N (1?g/day; 7 days) did not affect SBP or Na+ excretion significantly but increased GPR83 and decreased GRK4 expression in the kidney. The peptides PEN (proline, glutamic acid, and asparagine) and SAAS (serine, alanine, alanine, and serine) are derived from enzymatic breakdown of Pro-SAAS. Renal restricted infusion of PEN (1?g/day; 7 days) did not affect SBP, slightly decreased Na+ excretion and slightly increased GRK4 expression but did not affect GPR83 expression. In contrast, renal-restricted infusion of SAAS (1?g/day; 7 days) in mice decreased the SBP (82? vs 100? mmHg; P<0.05) with an increased mRNA expression of GPR83 (4.60?0.03 vs 1.0?0.01 fold; P<0.05), whereas GRK4 expression or Na+ excretion did not change significantly. PCSK1N expression was increased by a high salt diet (4%NaCl) in non-transgenic mice but was decreased in the salt sensitive GRK4 486V mice on the same diet. Our result suggested that Pro-SAAS peptides may be involved in the development of salt sensitivity through a gene-gene interaction between PCSK1N, GPR83 and GRK4.

Dopamine receptors D2 play a significant role in the kidney by maintaining the blood pressure (BP) and preventing renal inflammation and injury. Knockdown of dopamine receptor D2 in the mouse kidney increases BP and promotes renal inflammation. To study the effects of D2R in the mouse renal proximal tubule we generated Drd2 fl/fl,PSGLT2::Cre+mice (D2R PT-/-) that lack D2R only in the renal proximal tubule and Drd2 fl/fl,PSGLT2::Cre-(D2R PT+/+) mice that do not have the deletion. We studied male and female mice on normal salt (NS; 0.4% NaCl) and high salt diet (HS; 4% NaCl). Mice were genotyped for Drd2 fl/fland a smaller amplicon representing the Cre deletion mutant. On NS male D2R PT-/-had higher BP measured under anesthesia than male D2R PT+/+mice (113?1 vs 102?3 mmHg, n=5/group; P<0.05) and female D2R PT-/(103.8?5 mmHg) or D2R PT+/+(105.75?3 mmHg). BP on HS was similar in D2R PT-/-females and males. On normal salt diet renal mRNA expression of TNF-?, TGF?1, Fn1 and Col1a1 was higher (P<0.01) in females D2R PT+/+than in males D2R PT+/+conversely the expression of the kidney injury marker, Kim-1, was higher in males D2R PT+/+than in females (P<0.01). Males D2R PT-/-expressed less (P<0.01) renal TNF-?, TGF?1, Col1a1, cell proliferation marker Mki-67, and Fn1 than female D2R PT-/-. However, the expression of Kim-1 was less (P<0.01) in females D2R PT-/-.than in males. On HS, renal mRNA expression of TNF-?, TGF?1 and Fn-1 was similar in both males and females D2R PT+/+and D2R PT-/-. HS increased (P<0.05) the expression of Col1a1 and Kim-1 in males D2R PT+/+and D2R PT-/-but not in females of the two genotypes and also increased the expression of Mki-67 in D2R PT-/-males. Our data show striking differences in the inflammatory response, cell proliferation and kidney injury between males and females with females expressing more inflammatory and proliferation markers but less injury than males. Deletion of the D2R in the proximal tubule increases the renal expression of extracellular matrix proteins and inflammatory and proliferation markers. These effects are more pronounced in females that however show less Kim-1. The differences between males and females are maintained when on HS indicating that female mice have a ?healthier? response to renal injury.

We measured daily urinary excretion rates of dopamine and dopa during dietary salt loading and natriuretic responses to exogenous dopamine in Dahl salt-sensitive (DS), Dahl salt-resistant (DR) and Sprague-Dawley rats. Excretion rates of dopa increased approximately sixfold during salt loading in all rat strains. Maximal urinary dopa responses were attained within 1 day of salt loading. Daily excretion rates of dopamine also increased about five- to sixfold in DS and DR rats and about twofold in Sprague-Dawley rats, with maximal dopamine responses attained by day 5. Dopamine infusion (3|xg/kg per min) increased urinary sodium excretion by 406 ± 132 (mean ± s.e.m.) in Sprague-Dawley rats but only 267 ± 131 and 147 ± 80 in DS and DR rats (P<0.05 for Sprague-Dawley versus Dahl rats). The results demonstrate that salt loading markedly and rapidly increases dopa excretion in rats. Considering values for dopamine excretion in other rat strains, the results suggest that Dahl rats have increased formation of dopamine for a given amount of dopa delivery to the kidney and that this abnormality is unrelated to salt-sensitive hypertension in DS rats. The results also provide in vivo support for the view that the responsiveness of renal dopamine receptors mediating natriuresis is related to production of endogenous dopamine in the kidney

Shortterm treatment with clenbuterol 0.6 mgkg1subcutaneously s.c. daily produces a pressor effect in stressed rats after a period of immobilization 40 min. The stress applied markedly increases the plasma concentrations of norepinephrine NE and epinephrine. After bilateral adrenal demedullation, the increased levels of catecholamines and the hypertensive response obtained after clenbuterol treatment in the stressed animals were reduced to the values of the control rats. Clenbuterol treatment produced desensitization of the 2adrenoceptormediated effect and thus reduced the vasodilator response induced by isoproterenol and increased the vasoconstriction produced by epinephrine but not that caused by NE. This desensitization may be responsible for the hypertensive response after clenbuterol treatment in stressed animals which is attenuated after adrenal demedullation. In conclusion, our results provide evidence that clenbuterol treatment induces pressor effect in normotensive animals under stress.