Units length of fluid column, nl total fluid volume collected, min collection time, flow flow rate (nl/min), Ucpm I125 counts per minute in total fluid volume, Bkg I125 background, column H net cpm (Ucpm-Bkg), TF tubular fluid (cpm/nl). P plasma (cpm/nl), TF/P ratio tubular fluid cpm divided by plasma cpm, SNGFR single nephron GFR (TF/P x flow rate), absorption fluid reabsorption (SNGFR - flow rate), % Del fluid delivered to collection site in % of SNGFR, % Abs fluid absorption in % of SNGFR, MAP mean arterial pressure during collection. U urine (cpm in 2 duplicates), P plasma (cpm in 2 samples in duplicates).

Both sodium reabsorption in the thick ascending limb of the loop of Henle (TAL) and macula densa salt sensing crucially depend on the function of the Na/K/2Cl cotransporter NKCC2. The NKCC2 gene gives rise to at least three different full-length NKCC2 isoforms derived from differential splicing. In the present study, we addressed the influence of dietary salt intake on the differential splicing of NKCC2. Mice were subjected to diets with low-salt, standard salt, and high-salt content for 7 days, and NKCC2 isoform mRNA abundance was determined. With decreasing salt intake, we found a reduced abundance of the low-affinity isoform NKCC2A and an increase in the high-affinity isoform NKCC2B in the renal cortex and the outer stripe of the outer medulla. This shift from NKCC2A to NKCC2B during a low-salt diet could be mimicked by furosemide in vivo and in cultured kidney slices. Furthermore, the changes in NKCC2 isoform abundance during a salt-restricted diet were partly mediated by the actions of angiotensin II on AT1 receptors, as determined using chronic angiotensin II infusion. In contrast to changes in oral salt intake, water restriction (48 h) and water loading (8% sucrose solution) increased and suppressed the expression of all NKCC2 isoforms, without changing the distribution pattern of the single isoforms. In summary, the differential splicing of NKCC2 pre-mRNA is modulated by dietary salt intake, which may be mediated by changes in intracellular ion composition. Differential splicing of NKCC2 appears to contribute to the adaptive capacity of the kidney to cope with changes in reabsorptive needs.

Units length of fluid column, nl total fluid volume collected, min collection time, flow flow rate (nl/min), Ucpm I125 counts per minute in total fluid volume, Bkg I125 background, column H net cpm (Ucpm-Bkg), TF tubular fluid (cpm/nl). P plasma (cpm/nl), TF/P ratio tubular fluid cpm divided by plasma cpm, SNGFR single nephron GFR (TF/P x flow rate), absorption fluid reabsorption (SNGFR - flow rate), % Del fluid delivered to collection site in % of SNGFR, % Abs fluid absorption in % of SNGFR, MAP mean arterial pressure during collection. U urine (cpm in 2 duplicates), P plasma (cpm in 2 samples in duplicates).

Units length of fluid column, nl total fluid volume collected, min collection time, flow flow rate (nl/min), Ucpm I125 counts per minute in total fluid volume, Bkg I125 background, column H net cpm (Ucpm-Bkg), TF tubular fluid (cpm/nl). P plasma (cpm/nl), TF/P ratio tubular fluid cpm divided by plasma cpm, SNGFR single nephron GFR (TF/P x flow rate), absorption fluid reabsorption (SNGFR - flow rate), % Del fluid delivered to collection site in % of SNGFR, % Abs fluid absorption in % of SNGFR, MAP mean arterial pressure during collection. U urine (cpm in 2 duplicates), P plasma (cpm in 2 samples in duplicates).

Participation of connexin 40 (Cx40) in the regulation of renin secretion and in the tubuloglomerular feedback (TGF) component of renal autoregulation suggests that gap junctional coupling through Cx40 contributes to the function of the juxtaglomerular apparatus. In the present experiments, we determined the effect of targeted Cx40 deletion in C57BL/6 and FVB mice on TGF responsiveness. In C57BL/6 mice, stop-flow pressure (PSF) fell from 40.3 ± 2 to 34.5 ± 2 mmHg in wild-type (WT) and from 31 ± 1.06 to 26.6 ± 0.98 mmHg in Cx40-/- mice. PSF changes of 5.85 ± 0.67 mmHg in WT and of 4.3 ± 0.55 mmHg in Cx40-/- mice were not significantly different (P = 0.08). In FVB mice, PSF fell from 37.4 ± 1.5 to 31.6 ± 1.5 mmHg in WT and from 28.1 ± 1.6 to 25.4 ± 1.7 mmHg in Cx40-/-, with mean TGF responses being significantly greater in WT than Cx40-/- (5.5 ± 0.55 vs. 2.7 ± 0.84 mmHg; P = 0.002). In both genetic backgrounds, PSF values were significantly lower in Cx40-/- than WT mice at all flow rates. Arterial blood pressure in the animals prepared for micropuncture was not different between WT and Cx40-/- mice. We conclude that the TGF response magnitude in superficial cortical nephrons is reduced by 30-50% in mice without Cx40, but that with the exception of a small number of nephrons, residual TGF activity is maintained. Thus gap junctional coupling appears to modulate TGF, perhaps by determining the kinetics of signal transmission.

An increase of glomerular filtration rate (hyperfiltration) is an early functional change associated with type I or type II diabetes mellitus in patients and animal models. The causes underlying glomerular hyperfiltration are not entirely clear. There is evidence from studies in the streptozotocin model of diabetes in rats that an increase of proximal tubular reabsorption results in the withdrawal of a vasoconstrictor input exerted by the tubuloglomerular feedback (TGF) mechanism. In the present study, we have used micropuncture to assess single nephron function in wild type (WT) mice and in two strains of type I diabetic Ins2+/- mice in either a C57Bl/6 (Akita) or an A1AR-/- background (Akita/A1AR-/-) in which TGF is non-functional. Kidney glomerular filtration rate (GFR) of anesthetized mice was increased by 25% in Akita mice and by 52% in Akita/A1AR-/-, but did not differ between genotypes when corrected for kidney weight. Single nephron GFR (SNGFR) measured by end-proximal fluid collections averaged 11.8 ± 1 nl/min (n=17), 13.05 ± 1.1 nl/min (n=23; p=0.27), and 15.4 ± 0.84 nl/min (n=26; p=0.009 compared to WT; p=0.09 compared to Akita) in WT, Akita, and Akita/A1AR-/- mice respectively. Proximal tubular fluid reabsorption was not different between WT and diabetic mice and correlated with SNGFR in all genotypes. We conclude that glomerular hyperfiltration is a primary event in the Akita model of type I diabetes, perhaps driven by an increased filtering surface area, and that it is ameliorated by TGF to the extent that this regulatory system is functional.

WNK3 kinase is expressed throughout the nephron and acts as a positive regulator of NKCC2 and NCC in vitro. Here we addressed the in vivo relevance of WNK3 using WNK3-deficient mice. WNK3-/- mice were viable and showed no gross abnormalities. The net tubular function was similar in wild-type (WT) and WNK3-/- mice as assessed by determination of 24-h urine output (1.63 ± .06 in WT and 1.55 ± .1 ml in WNK3-/-, n=16; P=0.42) and ambient urine osmolarity (1,804 ± 62 in WT vs. 1,819 ± 61 mosmol/kg in WNK3-/-, n=40; P=0.86). Water restriction (48 h) increased urine osmolarity similarly in both genotypes to 3,440 ± 220 and 3,200 ± 180 mosmol/kg in WT and WNK3-/- mice, respectively (n=11; P=0.41). The glomerular filtration rate (343 ± 22 vs. 315 ± 13 ml/min), renal blood flow (1.35 ± 0.1 vs. 1.42 ± 0.04 ml), and plasma renin concentration (94 ± 18 vs. 80 ± 13 ng ANG I·ml(-1)·h(-1)) were similar between WT and WNK3-/- mice (n=13; P=0.54). WNK1 was markedly upregulated in WNK3-deficient mice, whereas the expression of WNK4 was similar in both genotypes. When the mice were fed a salt-restricted diet [0.02% NaCl (wt/wt)] the levels of pSPAK/OSR1, pNKCC2, and pNCC were enhanced in both genotypes compared with the baseline conditions, with the levels in WNK3-/- exceeding those in WT mice. The upregulation of pSPAK/OSR1, pNKCC2, and pNCC in WNK3-/- mice relative to the levels in WT mice when fed a low-salt diet was paralleled by an increased diuresis in response to hydrochlorothiazide. In summary, the overall relevance of WNK3 for the renal reabsorption of NaCl appears to be limited and can be largely compensated for by the activation of WNK3-independent pathways. Consequently, our data suggest that WNK3 may serve as a member of a kinase network that facilitates the fine-tuning of renal transepithelial NaCl transport.

The gap junctional protein connexin 40 (Cx40) is highly expressed in the extraglomerular mesangium connecting the tubular epithelium at the macula densa and the afferent arteriole. Participation of Cx40 in juxtaglomerular communication is suggested by the finding that the expression of renin and the localization of renin‐expressing cells are greatly abnormal in Cx40‐deficient mice. In the present experiments we have therefore used wild type and Cx40−/− mice to determine the role of connexin 40 in tubuloglomerular feedback (TGF). Stop flow pressure (Psf) assessed by micropuncture fell from 40.0±1.7 to 34.5±1.7 mmHg in C57Bl/6 wild type mice, and from 31.3±1.0 to 26.9±0.9 mmHg in Cx40−/− mice. Psf changes of 5.5±0.5 mmHg in wild type and of 4.4±0.5 in Cx40−/− mice were not significantly different (p=0.125). Psf values were significantly lower in Cx40−/− than wild type mice at all flow rates. Arterial blood pressure was not different between wild type and Cx40−/− mice. Glomerular filtration rate (GFR) of conscious mice was lower in Cx40−/− than wild types and this difference increased with aging. We conclude that TGF responsiveness is well maintained in the absence of connexin 40 suggesting that coupling through this dominant mesangial protein is not required for tubulo‐vascular communication. Renal vascular resistance appears to be elevated in Cx40−/− mice, perhaps a consequence of the elevated plasma renin levels.

The angiotensin receptor-associated protein (Atrap) interacts with angiotensin II (AngII) type 1 (AT1) receptors and facilitates their internalization in vitro, but little is known about the function of Atrap in vivo. Here, we detected Atrap expression in several organs of wild-type mice; the highest expression was in the kidney where it localized to the proximal tubule, particularly the brush border. There was no Atrap expression in the renal vasculature or juxtaglomerular cells. We generated Atrap-deficient (Atrap-/-) mice, which were viable and seemed grossly normal. Mean systolic BP was significantly higher in Atrap-/- mice compared with wild-type mice. Dose-response relationships of arterial BP after acute AngII infusion were similar in both genotypes. Plasma volume was significantly higher and plasma renin concentration was markedly lower in Atrap-/- mice compared with wild-type mice. (125)I-AngII binding showed enhanced surface expression of AT1 receptors in the renal cortex of Atrap-/- mice, accompanied by increased carboanhydrase-sensitive proximal tubular function. In summary, Atrap-/- mice have increased arterial pressure and plasma volume. Atrap seems to modulate volume status by acting as a negative regulator of AT1 receptors in the renal tubules.

Angiotensin II converting enzyme inhibitors (ACEI) or angiotensin II receptor blockers (ARB) presumably stimulate renin secretion by interrupting angiotensin II feedback inhibition. The increase in cytosolic calcium caused by activation of Gq-coupled AT1 receptors may mediate the renin-inhibitory effect of angiotensin II at the cellular level, implying that ACEI and ARB may work by reducing intracellular calcium. Here, we investigated whether angiotensin II blockade acts predominantly through Gs-mediated stimulation of adenylyl cyclase (AC) by testing the effect of ACEI and ARB in mice with juxtaglomerular cell-specific deficiency of the AC-stimulatory Gsalpha. The ACEI captopril and quinaprilate and the ARB candesartan significantly increased plasma renin concentration (PRC) to 20 to 40 times basal PRC in wild-type mice but did not significantly alter PRC in Gsalpha-deficient mice. Captopril also completely abrogated renin stimulation in wild-type mice after co-administration of propranolol, indomethacin, and L-NAME. Treatment with enalapril and a low-NaCl diet for 7 days led to a 35-fold increase in PRC among wild-type mice but no significant change in PRC among Gsalpha-deficient mice. Three different pharmacologic inhibitors of AC reduced the stimulatory effect of captopril by 70% to 80%. In conclusion, blockade of angiotensin II stimulates renin synthesis and release indirectly through the action of ligands that activate the cAMP/PKA pathway in a Gsalpha-dependent fashion, including catecholamines, prostaglandins, and nitric oxide.

During metanephric kidney development, renin expression in the renal vasculature begins in larger vessels, shifting to smaller vessels and finally remaining restricted to the terminal portions of afferent arterioles at the entrance into the glomerular capillary network. The mechanisms determining the successive expression of renin along the vascular axis of the kidney are not well understood. Since the cAMP signaling cascade plays a central role in the regulation of both renin secretion and synthesis in the adult kidney, it seemed feasible that this pathway might also be critical for renin expression during kidney development. In the present study we determined the spatiotemporal development of renin expression and the development of the preglomerular arterial tree in mouse kidneys with renin cell-specific deletion of G(s)alpha, a core element for receptor activation of adenylyl cyclases. We found that in the absence of the G(s)alpha protein, renin expression was largely absent in the kidneys at any developmental stage, accompanied by alterations in the development of the preglomerular arterial tree. These data indicate that the maintenance of renin expression following a specific spatiotemporal pattern along the preglomerular vasculature critically depends on the availability of G(s)alpha. We infer from our data that the cAMP signaling pathway is not only critical for the regulation of renin synthesis and secretion in the mature kidney but that it also is critical for establishing the juxtaglomerular expression site of renin during development.

Adenosine 1 receptors (A1AR) in the kidney are expressed in the vasculature and the tubular system. Pharmacological inhibition or global genetic deletion of A1AR causes marked reductions or abolishment of tubuloglomerular feedback (TGF) responses. To assess the function of vascular A1AR in TGF, we generated transgenic mouse lines in which A1AR expression in smooth muscle was augmented by placing A1AR under the control of a 5.38-kb fragment of the rat smooth muscle alpha-actin promoter and first intron (12). Two founder lines with highest expression in the kidney [353 +/- 42 and 575 +/- 43% compared with the wild type (WT)] were used in the experiments. Enhanced expression of A1AR at the expected site in these lines was confirmed by augmented constrictor responses of isolated afferent arterioles to administration of the A1AR agonist N6-cyclohexyladenosine. Maximum TGF responses (0-30 nl/min flow step) were increased from 8.4 +/- 0.9 mmHg in WT (n = 21) to 14.2 +/- 0.7 mmHg in A1AR-transgene (tg) 4 (n = 22; P < 0.0001), and to 12.6 +/- 1.2 mmHg in A1AR-tg7 (n = 12; P < 0.02). Stepwise changes in perfusion flow caused greater numerical TGF responses in A1AR-tg than WT in all flow ranges with differences reaching levels of significance in the intermediate flow ranges of 7.5-10 and 10-15 nl/min. Proximal-distal single-nephron glomerular filtration rate (SNGFR) differences (free-flow micropuncture) were also increased in A1AR-tg, averaging 6.25 +/- 1.5 nl/min compared with 2.6 +/- 0.51 nl/min in WT (P = 0.034). Basal plasma renin concentrations as well as the suppression of renin secretion after volume expansion were similar in A1AR-tg and WT mice, suggesting lack of transgene expression in juxtaglomerular cells. These data indicate that A1AR expression in vascular smooth muscle cells is a critical component for TGF signaling and that changes in renal vascular A1AR expression may determine the magnitude of TGF responses.

Atrap is an interacting protein of angiotensin AT1 receptors and was shown to facilitate AT1 receptor internalization in vitro. To further assess the in vivo function of Atrap, we generated Atrap‐deficient mice by gene targeting.Atrap‐deficient mice were viable, fertile and showed no gross abnormalities. Atrap protein in the kidney was localized to the proximal tubules. We found no Atrap expression in the renal vasculature or in JG cells. Systolic arterial blood pressure (telemetry) was elevated in Atrap‐/‐ compared to +/+ mice averaging 120.3±0.7 vs. 111.7±1.4 mm Hg (n=5, 72 hrs‐measurement, p=0.001). Dose‐response curves of arterial blood pressure after bolus angiotensin II infusion were similar in both genotypes. Plasma renin concentration (PRC) was markedly reduced in Atrap‐/‐ compared to +/+ (49±4 vs. 100±13 ng Ang I/mL/hr, n=40 and 37, respectively; p<0.001). After acute furosemide administration PRC increased 13.2±2 fold in Atrap‐/‐ and 9.9±1.8 fold in +/+ (p=0.34) indicating an intact renin secretory capacity in Atrap‐/‐ mice. Plasma volume was increased in Atrap‐/‐ compared to wild types (4.1±0.2 vs. 3.1±0.2% of body weight, n=18 and 13; p<0.002).In summary, Atrap‐deficient mice are hypertensive, volume expanded, and show a suppressed renin system. We suggest that Atrap acts as a negative regulator of AT1 receptors and that Atrap may be involved in the control of proximal tubular function.

Intraglomerular hypertension and glomerular hyperfiltration likely contribute to the pathogenesis of diabetic nephropathy, and tubuloglomerular feedback (TGF) has been suggested to play a role in diabetic hyperfiltration. A1 adenosine receptor (A1AR) null mice lack a TGF response, so this model was used to investigate the contribution of TGF to hyperfiltration in diabetic Ins2(+/-) Akita mice. TGF responses in Ins2(+/-) A1AR(-/-) double mutants were abolished, whereas they were attenuated in Ins2(+/-) mice. GFR, assessed at 14, 24, and 33 wk, was approximately 30% higher in Ins2(+/-) than in wild-type (WT) mice and increased further in Ins2(+/-) A1AR(-/-) mutants (P < 0.01 versus both WT and Ins2(+/-) mice at all ages). Histologic evidence of glomerular injury and urinary albumin excretion were more pronounced in double-mutant than single-mutant or WT mice. In summary, the marked elevation of GFR in diabetic mice that lack a TGF response indicates that TGF is not required to cause hyperfiltration in the Akita model of diabetes. Rather, an A1AR-dependent mechanism, possibly TGF, limits the degree of diabetic hyperfiltration and nephropathy.

Studies in mice with null mutations of adenosine 1 receptor or ecto-5'-nucleotidase genes suggest a critical role of adenosine and its precursor 5'-AMP in tubulovascular signaling. To assess whether the source of juxtaglomerular nucleotides can be traced back to ATP dephosphorylation, experiments were performed in mice with a deficiency in NTPDase1/CD39, an ecto-ATPase catalyzing the formation of AMP from ATP and ADP. Urine osmolarity and glomerular filtration rate (GFR) were indistinguishable between NTPDase1/CD39(-/-) and wild-type (WT) mice. Maximum tubuloglomerular feedback (TGF) responses, as determined by proximal tubular stop flow pressure measurements, were reduced in NTPDase1/CD39(-/-) mice compared with controls (4.2 +/- 0.9 vs. 10.5 +/- 1.2 mmHg, respectively; P = 0.0002). Residual TGF responses gradually diminished after repeated changes in tubular perfusion flow averaging 2.9 +/- 0.9 (on response) and 3.5 +/- 1.1 (off response) mmHg after the second and 2.2 +/- 0.5 (on response) and 1.5 +/- 0.8 (off response) mmHg after the third challenge, whereas no fading of TGF responsiveness was observed in WT mice. Macula densa-dependent and pressure-dependent inhibition of renin secretion, as assessed by acute salt loading and phenylephrine injection, respectively, were intact in NTPDase1/CD39-deficient mice. In summary, NTPDase1/CD39-deficient mice showed a markedly compromised TGF regulation of GFR. These data support the concept of an extracellular dephosphorylation cascade during tubular-vascular signal transmission in the juxtaglomerular apparatus that is initiated by a regulated release of ATP from macula densa cells and results in adenosine-mediated afferent arteriole constriction.

To explore the role of NKCC1 in the regulation of renal hemodynamics we determined tubuloglomerular feedback (TGF) and renal blood flow (RBF) autoregulation in wild type (WT) and NKCC1‐deficient mice. Tissue‐specific basal renal blood flow (RBF) was similar in NKCC1−/− and WT mice (5.82 ± 0.27 vs. 6.20 ± 0.42 ml/min/g; p=.43), but absolute RBF was lower in NKCC1−/− as a result of a reduced kidney weight (479 vs. 603 mg; p=.003). Maximum TGF responses of stop flow pressure were markedly lower in NKCC1−/ − than WT mice (2.9 ± 0.4 vs. 12.4 ± 0.8 mmHg, p<.001) while blood pressure under anesthesia was identical (90 mm Hg). In vivo perfused loops of Henle (6 nl/min) showed unaltered distal [Cl] and absorption rates in NKCC1−/ − and WT mice (54.4 vs. 56.3 mEq/l; 719 vs. 728 pEq/min). Renal vascular resistance (RVR) of WT responded to a step increase of renal arterial pressure with a fast component (onset at 1 s, duration 6 s) and a slow component (onset at 7 s, duration 10 s) establishing full autoregulation (restoration of 100% of initial RBF) after 17s. In contrast, RVR adjustments in NKCC1−/ − mice were slower in onset and longer in duration reaching completion after 58 s. In summary, markedly reduced TGF and slower autoregulatory responses in NKCC1−/ − mice suggest that NKCC1‐mediated ion fluxes are important for maintaining the contractility of renal resistance vessels.

We have recently generated a transgenic mouse line (termed hRen-Cre) that expresses Cre-recombinase under the control of a 12.2-kb fragment of the human renin promoter. In the present study, we have crossed hRen-Cre mice with a mouse strain in which exon 1 of the Gnas gene is flanked by loxP sites. Gnas encodes the α-subunit of the stimulatory G protein (Gsα). Our aim has been to generate a mouse model with locally restricted inactivation of Gsα to extend studies of the role of Gsα function in vivo. Mice with local Cre-mediated inactivation of Gsα (rCre-Gsα) are viable and fertile. Their most obvious phenotype consists of marked skeletal malformations of the forelimbs in which computer-tomography scans reveal shortened and fused extremity bones. Extraskeletal ossifications occur in the subcutis and in skeletal muscles associated with the affected long bones. Plasma calcium, phosphate and parathyroid hormone are normal. Skin histology has demonstrated diffuse mineralization and ossification associated with the basal cells of hair follicles. This phenotype in part resembles syndromes in humans associated with loss-of-function of Gsα, such as Albright hereditary osteodystrophy and progressive osseous heteroplasia. The renal phenotype of rCre-Gsα mice is inconspicuous. Plasma renin concentration, ambient urine osmolarity, and the glomerular filtration rate of rCre-Gsα mice do not differ from controls. The absence of measurable functional changes in the renin-angiotensin system indicates insufficient Cre expression in juxtaglomerular granular cells in this strain of mice. Nevertheless, the present report reaffirms the importance of Gsα signaling for bone development and the suppression of ectopic ossification.

The present experiments were performed in β1/β2-adrenergic receptor–deficient mice (β1/β2ADR −/− ) to assess the role of β-adrenergic receptors in basal and regulated renin expression and release. On a control diet, plasma renin concentration (in ng angiotensin I per mL per hour), determined in tail vein blood, was significantly lower in β1/β2ADR −/− than in wild-type (WT) mice (222±65 versus 1456±335; P <0.01). Renin content and mRNA were 77% and 65±5% of WT. Plasma aldosterone (in picograms per mL) was also significantly reduced (420±36 in β1/β2ADR −/− versus 692±59 in WT). A low-salt diet (0.03%) for 1 week increased plasma renin concentration significantly in both β1/β2ADR −/− and WT mice (to 733±54 and 2789±555), whereas a high-salt diet (8%) suppressed it in both genotypes (to 85±24 in β1/β2ADR −/− and to 676±213 in WT). The absolute magnitude of salt-induced changes of plasma renin concentration was markedly greater in WT mice. Acute stimulation of renin release by furosemide, quinaprilat, captopril, or candesartan caused significant increases of plasma renin concentration in both β1/β2ADR −/− and WT mice, but again the absolute changes were greater in WT mice. We conclude that maintenance of normal levels of renin synthesis and release requires tonic β-adrenergic receptor activation. In the chronic absence of β-adrenergic receptor input, the size of the releasable renin pool decreases with a concomitant reduction in the magnitude of the plasma renin concentration changes caused by variations of salt intake or acute stimulation with furosemide, angiotensin-converting enzyme, or angiotensin type 1 receptor inhibition, but regulatory responsiveness is nonetheless maintained.

By crossing mice with expression of Cre recombinase under control of the endogenous renin promoter (Sequeira Lopez ML, Pentz ES, Nomasa T, Smithies O, Gomez RA. Dev Cell 6: 719-728, 2004) with mice in which exon 1 of the Gnas gene was flanked by loxP sites (Chen M, Gavrilova O, Liu J, Xie T, Deng C, Nguyen AT, Nackers LM, Lorenzo J, Shen L, Weinstein LS. Proc Natl Acad Sci USA), we generated animals with preferential and nearly complete excision of Gsalpha in juxtaglomerular granular (JG) cells. Compared with wild-type animals, mice with conditional Gsalpha deficiency had markedly reduced basal levels of renin expression and very low plasma renin concentrations. Furthermore, the acute release responses to furosemide, hydralazine, and isoproterenol were virtually abolished. Consistent with a state of primary renin depletion, Gsalpha-deficient mice had reduced arterial blood pressure, reduced levels of aldosterone, and a low glomerular filtration rate. Renin content and renin secretion of JG cells in primary culture were drastically reduced, and the stimulatory response to the addition of PGE(2) or isoproterenol was eliminated. Unexpectedly, Gsalpha recombination was also observed in the renal medulla, and this was associated with a vasopressin-resistant concentrating defect. Our study shows that Cre recombinase under control of the renin promoter can be used for the excision of floxed targets from JG cells. We conclude that Gsalpha-mediated signal transduction is essential and nonredundant in the control of renin synthesis and release.