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Effects of estradiol and progesterone on urine output and osmolality in OVX rats: Urine volume (absolute; A), urine output (corrected for body weight; B), and urinary osmolality (C) measured 1 day before OVX (1) and 2, 7, or 14 days post-OVX or sham surgery. Values are means SE of 7 rats/group. *P 0.05 OVX compared with sham-operated rats. #P 0.05 treated OVX group compared with untreated OVX rats.
Source publication
While there is evidence that sex hormones influence multiple systems involved in salt and water homeostasis, the question of whether sex hormones regulate aquaporin 2 (AQP2) and thus water handling by the collecting duct has been largely ignored. Accordingly, the present study investigated AQP2 expression, localization and renal water handling in i...
Citations
... AQP3 is localized in the basolateral membrane of principal cells in the connecting tubule and collecting duct, and together with AQP4, it represents the main exit pathway of water reabsorbed by AQP2 [2]. Several studies have shown that estrogen affects kidney-mediated water homeostasis [3][4][5], and we have previously demonstrated that estrogen affects the expression and trafficking of AQP2 in collecting-duct principal cells in rats subjected to ovariectomy [5]. In line with this, we have recently shown that tamoxifen (TAM), a selective estrogen receptor modulator (SERM), could rescue AQP2 expression and improve urinary concentration capacity in rats with lithium-induced nephrogenic diabetes insipidus (NDI) [6] as well as in rats subjected to unilateral ureteral obstruction (UUO) [7]. ...
... AQP3 is localized in the basolateral membrane of principal cells in the connecting tubule and collecting duct, and together with AQP4, it represents the main exit pathway of water reabsorbed by AQP2 [2]. Several studies have shown that estrogen affects kidney-mediated water homeostasis [3][4][5], and we have previously demonstrated that estrogen affects the expression and trafficking of AQP2 in collecting-duct principal cells in rats subjected to ovariectomy [5]. In line with this, we have recently shown that tamoxifen (TAM), a selective estrogen receptor modulator (SERM), could rescue AQP2 expression and improve urinary concentration capacity in rats with lithium-induced nephrogenic diabetes insipidus (NDI) [6] as well as in rats subjected to unilateral ureteral obstruction (UUO) [7]. ...
Sex hormones play an important role in the regulation of water homeostasis, and we have previously shown that tamoxifen (TAM), a selective estrogen receptor modulator (SERM), affects the regulation of aquaporin (AQP)-2. In this study, we investigated the effect of TAM on the expression and localization of AQP3 in collecting ducts using various animal, tissue, and cell models. The impact of TAM on AQP3 regulation was studied in rats subjected to 7 days of unilateral ureteral obstruction (UUO), with the rats fed a lithium-containing diet to induce nephrogenic diabetes insipidus (NDI), as well as in human precision-cut kidney slices (PCKS). Moreover, intracellular trafficking of AQP3 after TAM treatment was investigated in Madin-Darby Canine Kidney (MDCK) cells stably expressing AQP3. In all models, the expression of AQP3 was evaluated by Western blotting, immunohistochemistry and qPCR. TAM administration attenuated UUO-induced downregulation of AQP3 and affected the localization of AQP3 in both the UUO model and the lithium-induced NDI model. In parallel, TAM also affected the expression profile of other basolateral proteins, including AQP4 and Na/K-ATPase. In addition, TGF-β and TGF-β+TAM treatment affected the localization of AQP3 in stably transfected MDCK cells, and TAM partly attenuated the reduced AQP3 expression in TGF-β exposed human tissue slices. These findings suggest that TAM attenuates the downregulation of AQP3 in a UUO model and a lithium-induced NDI model and affects the intracellular localization in the collecting ducts.
... Apical AQP2 and serosal AQP3 levels were quantified by holding illumination, gain, sampling period, and other parameters constant and below saturation during the acquisition of high-magnification immunofluorescent images. Regions of interest were selected by drawing lines across the apical and basolateral membranes of labeled tubular cells following a semiquantitative analysis protocol (6). ImageJ software (National Institutes of Health) was used to find peak intensities for the estimation of corresponding plasma membrane levels. ...
The renin-angiotensin-aldosterone and arginine vasopressin-V2 receptor-aquaporin-2 systems converge upon the epithelial sodium channel ENaC to regulate blood pressure and plasma tonicity. While it is established that V2 receptors initiate renal water reabsorption through aquaporin-2, whether V2 receptors can also induce renal sodium retention through ENaC and raise blood pressure remains an open question. We hypothesized that a specific increase in V2 receptor mediated ENaC activity can lead to high blood pressure. Our approach was to test effects of chronic activation of V2 receptors in Liddle mice, a genetic mouse model of high ENaC activity, and compare differences in ENaC activity, urine sodium excretion, and blood pressure with control mice. We found that ENaC activity was elevated in Liddle mice and could not be stimulated further by administration of dDAVP, a V2 receptor specific agonist. In contrast, Liddle mice showed higher levels of expression of AQP2 and AQP3, but they could still respond to dDAVP infusion by increasing p-AQP2 expression. With dDAVP infusion, Liddle mice excreted smaller urine volume, less urine sodium, and developed higher blood pressure compared with control mice; this hypertension was attenuated with administration of the ENaC inhibitor benzamil. We conclude that V2 receptors contribute to hypertension in the Liddle mouse model by promoting primary sodium and concomitant water retention.
... V2 receptor activation induces water absorption and sodium retention through aquaporin 2 (AQP2) gene expression stimulation and protein translocation to the apical membrane of the principal cells of the kidney collecting duct (11,13). The process of AQP2-bearing vesicles docking and fusion to the apical plasma membrane as well as the exocytosis/endocytosis balance are tightly regulated by ADH through posttranslational modifications such as phosphorylation, ubiquitylation, and degradation (14); other factors such as prostaglandin E2, estrogen, and interstitial medullary hypertonicity per se can also affect AQP2 expression and trafficking independently from ADH (15)(16)(17)(18)(19). In addition to direct transcellular water transport, ADH contributes to interstitial intramedullary hyperosmolality and allows gradient-driven water absorption by increasing sodium absorption in several other tubular segments [thick-ascending limb of Henle-luminal Na-K-2Cl cotransporter (NKCC2) and basolateral alpha-1-Na-K ATPase, distal convoluted tubulesNa-Cl co-transporter (NCC), and collecting ducts-epithelial sodium channel (ENaC)] and by favoring urea cycling and interstitial urea medullary absorption (increased expression of urea medullary transporters A1 and A3) (20,21). ...
In addition to long-term regulation of blood pressure (BP), in the kidney resides the initial trigger for hypertension development due to an altered capacity to excrete sodium and water. Betaine is one of the major organic osmolytes, and its betaine/gamma-aminobutyric acid transporter (BGT-1) expression in the renal medulla relates to interstitial tonicity and urinary osmolality and volume. This study investigated altered water and sodium balance as well as changes in antidiuretic hormone (ADH) activity in female spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats from their 3–5 weeks of age (prehypertensive phase) to SHR’s 28–30 weeks of age (established hypertension-organ damage). Young prehypertensive SHRs showed a reduced daily urine output, an elevated urine osmolarity, and higher immunostaining of tubule BGT-1, alpha-1-Na-K ATPase in the outer medulla vs. age-matched WKY. ADH circulating levels were not different between young prehypertensive SHR and WKY, but the urine aquaporin2 (AQP2)/creatinine ratio and labeling of AQP2 in the collecting duct were increased. At 28–30 weeks, hypertensive SHR with moderate renal failure did not show any difference in urinary osmolarity, urine AQP2/creatinine ratio, tubule BGT-1, and alpha-1-Na-K ATPase as compared with WKY. These results suggest an increased sensitivity to ADH in prehypertensive female SHR. On this basis, a second series of experiments were set to study the role of ADH V1 and V2 receptors in the development of hypertension, and a group of female prehypertensive SHRs were treated from the 25th to 49th day of age with either V1 (OPC21268) or V2 (OPC 41061) receptor antagonists to evaluate the BP time course. OPC 41061-treated SHRs had a delayed development of hypertension for 5 weeks without effect in OPC 21268-treated SHRs. In prehypertensive female SHR, an increased renal ADH sensitivity is crucial for the development of hypertension by favoring a positive water balance. Early treatment with selective V2 antagonism delays future hypertension development in young SHRs.
... 4,[23][24][25][26] It has also been shown that estrogen supplementation to ovariectomized rats increases water intake and urine flow. 27 Notably, pretreatment with angiotensin II decreased water intake in male but not female rats. 28 Central interactions between estrogen and angiotensin II control the drinking behavior in rats. ...
Background
Premenopausal women are less likely to develop hypertension and salt‐related complications than are men, yet the impact of sex on mechanisms regulating Na ⁺ homeostasis during dietary salt challenges is poorly defined. Here, we determined whether female rats have a more efficient capacity to acclimate to increased dietary salt intake challenge.
Methods and Results
Age‐matched male and female Sprague Dawley rats maintained on a normal‐salt (NS) diet (0.49% NaCl) were challenged with a 5‐day high‐salt diet (4.0% NaCl). We assessed serum, urinary, skin, and muscle electrolytes; total body water; and kidney Na ⁺ transporters during the NS and high‐salt diet phases. During the 5‐day high‐salt challenge, natriuresis increased more rapidly in females, whereas serum Na ⁺ and body water concentration increased only in males. To determine if females are primed to handle changes in dietary salt, we asked the question whether the renal endothelin‐1 natriuretic system is more active in female rats, compared with males. During the NS diet, female rats had a higher urinary endothelin‐1 excretion rate than males. Moreover, Ingenuity Pathway Analysis of RNA sequencing data identified the enrichment of endothelin signaling pathway transcripts in the inner medulla of kidneys from NS‐fed female rats compared with male counterparts. Notably, in human subjects who consumed an Na ⁺ ‐controlled diet (3314–3668 mg/day) for 3 days, women had a higher urinary endothelin‐1 excretion rate than men, consistent with our findings in NS‐fed rats.
Conclusions
These results suggest that female sex confers a greater ability to maintain Na ⁺ homeostasis during acclimation to dietary Na ⁺ challenges and indicate that the intrarenal endothelin‐1 natriuretic pathway is enhanced in women.
... Various alternative receptors also appear to impact AQP2 as well (reviewed in [48]). These include the farnesoid X receptor [49], the peroxisome proliferator-activated receptor-γ [50], angiotensin II receptor type I [51], the bile acid receptor TGR5 [49], the glucocorticoid and mineralocorticoid receptors [52], the estrogen receptor-α [53], and the liver X receptor-β [48]. ...
As a rare hereditary disease, congenital nephrogenic diabetes insipidus (NDI) is clinically characterized by polyuria with hyposthenuria and polydipsia. NDI results from collecting duct principal cell hyporesponsiveness or insensitivity to the antidiuretic action of arginine vasopressin (AVP). The principal cell-specific water channel aquaporin-2 (AQP2) plays an essential role in water reabsorption along osmotic gradients. The capacity to accumulate AQP2 in the apical plasma membrane in response to decreased fluid volume or increased plasma osmolality is critically regulated by the antidiuretic hormone AVP and its receptor 2 (AVPR2). Mutations in AVPR2 result in X-linked recessive NDI, the most common form of inherited NDI. Genetic defects in AQP2 cause autosomal recessive or dominant NDI. In this review, we provide an updated overview of the genetic and molecular mechanisms of congenital NDI, with a focus on the potential disease-causing mutations in AVPR2 and AQP2, the molecular defects in the AVPR2 and AQP2 mutants, post-translational modifications (i.e., phosphorylation, ubiquitination, and glycosylation) and various protein-protein interactions that regulate phosphorylation, ubiquitination, tetramerization, trafficking, stability, and degradation of AQP2.
... Binding studies using radiolabeled E 2 revealed that radioactivity localizes to the proximal tubule and the inner medullary collecting duct [45], which is relevant to our findings in mIMCD3 cells. Data showed that classical ER, ERα, and ERβ, and membrane-associated ER, G protein-coupled ER, are expressed in the collecting ducts [46]. However, the exact relationship between the ER and P2 signaling systems in the kidney is not clear. ...
Background:
Premenopausal women have a lower risk of hypertension compared to age-matched men and postmenopausal women. P2Y2 and P2Y4 purinoceptor can be considered potential contributors to hypertension due to their emerging roles in regulating renal tubular Na+ transport. Activation of these receptors inhibits epithelial Na+ channel activity (ENaC) via a phospholipase C (PLC)-dependent pathway resulting in natriuresis. We recently reported that activation of P2Y2 and P2Y4 receptors in the renal medulla by UTP promotes natriuresis in male and ovariectomized (OVX) rats, but not in ovary-intact females. This led us to hypothesize that ovary-intact females have greater basal renal medullary activity of P2 (P2Y2 and P2Y4) receptors regulating Na+ excretion compared to male and OVX rats.
Methods:
To test our hypothesis, we determined (i) the effect of inhibiting medullary P2 receptors by suramin (750 μg/kg/min) on urinary Na+ excretion in anesthetized male, ovary-intact female, and OVX Sprague Dawley rats, (ii) mRNA expression and protein abundance of P2Y2 and P2Y4 receptors, and (iii) mRNA expression of their downstream effectors (PLC-1δ and ENaCα) in renal inner medullary tissues obtained from these three groups. We also subjected cultured mouse inner medullary collecting duct cells (segment 3, mIMCD3) to different concentrations of 17ß-estradiol (E2, 0, 10, 100, and 1000 nM) to test whether E2 increases mRNA expression of P2Y2 and P2Y4 receptors.
Results:
Acute P2 inhibition attenuated urinary Na+ excretion in ovary-intact females, but not in male or OVX rats. We found that P2Y2 and P2Y4 mRNA expression was higher in the inner medulla from females compared to males or OVX. Inner medullary lysates showed that ovary-intact females have higher P2Y2 receptor protein abundance, compared to males; however, OVX did not eliminate this sex difference. We also found that E2 dose-dependently upregulated P2Y2 and P2Y4 mRNA expression in mIMCD3.
Conclusion:
These data suggest that ovary-intact females have enhanced P2Y2 and P2Y4-dependent regulation of Na+ handling in the renal medulla, compared to male and OVX rats. We speculate that the P2 pathway contributes to facilitated renal Na+ handling in premenopausal females.
... They claim that this difference is due to high androgen, low progesterone exposure. Cheema et al. (22) have shown that AQP2 expressions were elevated in ovariectomized rat kidneys. They also have shown that estrogen replacement had decreased AQP2 levels. ...
... Previous studies showed the existence of GPER mRNA and protein in the kidney. [7][8][9] Early studies demonstrated smooth muscle cells in renal pelvis and to a lesser extent the renal medulla. 9 However, multiple studies reported that GPER expression is mainly in tubular epithelial cells. ...
Background
The novel estrogen receptor, G‐protein–coupled estrogen receptor ( GPER ), is responsible for rapid estrogen signaling. GPER activation elicits cardiovascular and nephroprotective effects against salt‐induced complications, yet there is no direct evidence for GPER control of renal Na ⁺ handling. We hypothesized that GPER activation in the renal medulla facilitates Na ⁺ excretion.
Methods and Results
Herein, we show that infusion of the GPER agonist, G1, to the renal medulla increased Na ⁺ excretion in female Sprague Dawley rats, but not male rats. We found that GPER mRNA expression and protein abundance were markedly higher in outer medullary tissues from females relative to males. Blockade of GPER in the renal medulla attenuated Na ⁺ excretion in females. Given that medullary endothelin 1 is a well‐established natriuretic factor that is regulated by sex and sex steroids, we hypothesized that GPER activation promotes natriuresis via an endothelin 1–dependent pathway. To test this mechanism, we determined the effect of medullary infusion of G1 after blockade of endothelin receptors. Dual endothelin receptor subtype A and endothelin receptor subtype B antagonism attenuated G1‐induced natriuresis in females. Unlike males, female mice with genetic deletion of GPER had reduced endothelin 1, endothelin receptor subtype A, and endothelin receptor subtype B mRNA expression compared with wild‐type controls. More important, we found that systemic GPER activation ameliorates the increase in mean arterial pressure induced by ovariectomy.
Conclusions
Our data uncover a novel role for renal medullary GPER in promoting Na ⁺ excretion via an endothelin 1–dependent pathway in female rats, but not in males. These results highlight GPER as a potential therapeutic target for salt‐sensitive hypertension in postmenopausal women.
... Binding studies using radiolabeled E 2 revealed that radioactivity localizes to the proximal tubule and the inner medullary collecting duct [45], which is relevant to our ndings in mIMCD3 cells. Data showed that classical ER, ERα and ERβ, and membrane-associated ER, G protein-coupled ER, are expressed in the collecting ducts [46]. However, the exact relationship between the ER and P2 signaling systems in the kidney is not clear. ...
Background: Premenopausal women have a lower risk of hypertension compared to age-matched men and postmenopausal women. P2Y2 and P2Y4 purinoceptor can be considered potential contributors to hypertension due to their emerging roles in regulating renal tubular Na⁺ transport. Activation of these receptors inhibits epithelial Na⁺ channel activity (ENaC) via a phospholipase C (PLC)-dependent pathway resulting in natriuresis. We recently reported that activation of P2Y2 and P2Y4 receptors in the renal medulla by UTP promotes natriuresis in male and ovariectomized (OVX) rats, but not in ovary-intact females. This led us to hypothesize that ovary-intact females have greater basal renal medullary activity of P2 (P2Y2 and P2Y4) receptors regulating Na⁺ excretion compared to male and OVX rats.
Methods: To test our hypothesis, we determined (i) the effect of inhibiting medullary P2 receptors by suramin (750 μg/kg/min) on urinary Na⁺ excretion in anesthetized male, ovary-intact female and OVX Sprague Dawley rats, (ii) mRNA expression and protein abundance of P2Y2 and P2Y4 receptors and (iii) mRNA expression of their downstream effectors (PLC-1d and ENaCa) in renal inner medullary tissues obtained from these three groups. We also subjected cultured mouse inner medullary collecting duct cells (segment 3, mIMCD3) to different concentrations of 17ß-estradiol (E2, 0, 10, 100 and 1000 nM) to test whether E2 increases mRNA expression of P2Y2 and P2Y4 receptors.
Results: Acute P2 inhibition attenuated urinary Na⁺ excretion in ovary-intact females, but not in male or OVX rats. We found that P2Y2 and P2Y4 mRNA expression was higher in the inner medulla from females compared to males or OVX. Inner medullary lysates showed that ovary-intact females have higher P2Y2 receptor protein abundance, compared to males, however, OVX did not eliminate this sex difference. We also found that E2 dose-dependently upregulated P2Y2 and P2Y4 mRNA expression in mIMCD3.
Conclusion: These data suggest that ovary-intact females have enhanced P2Y2 and P2Y4-dependent regulation of Na⁺ handling in the renal medulla, compared to male and OVX rats. We speculate that the P2 pathway contributes to facilitated renal Na⁺ handling in premenopausal females.
... Females ordinarily have higher levels of AVPR2 in the kidney compared to males (Liu et al. 2011). Ovariectomized female rats displayed higher phosphorylated-AQP2 in their kidneys, and in vitro studies have shown that direct estrogen stimulation of the mpkCCD principal cell line decreased renal AQP2 mRNA and protein (Cheema et al. 2015). Interestingly expression of ERa was shown to be important in mediating the inhibitory effect of oestradiol on AQP2 expression. ...
Maternal alcohol consumption can impair renal development and program kidney dysfunction in offspring. Given that most women who drink alcohol cease consumption upon pregnancy recognition, we aimed to investigate the effect of alcohol around the time of conception (PC:EtOH) on offspring renal development and function. Rats received a liquid diet ±12.5% v/v ethanol from 4 days before to 4 days after mating. At postnatal day 30, nephron number was assessed. Urine flow and electrolyte (Na, K, Cl) excretion was measured at 6 and 19 months and blood pressure at 12 months. At 19 months, kidneys were collected for gene and protein analysis and assessment of collecting duct length. At postnatal day 30, PC:EtOH offspring had fewer nephrons. At 6 months, PC:EtOH exposure did not alter urine flow nor affect blood pressure at 12 months. At 19 months, female but not male offspring exposed to PC:EtOH drank more water and had a higher urine flow despite no differences in plasma arginine vasopressin (AVP) concentrations. Aqp2 mRNA and Avpr2 mRNA and protein expression was increased in kidneys from female PC:EtOH offspring but collecting duct lengths were similar. Immunofluorescent staining revealed diffuse cytoplasmic distribution of AQP2 protein in kidneys from PC:EtOH females, compared with controls with apical AQP2 localization. PC:EtOH resulted in a low nephron endowment and in female offspring, associated with age-related diuresis. Changes in expression and cellular localization of AQP2 likely underpin this disturbance in water homeostasis and highlight the need for alcohol to be avoided in early pregnancy.
