Regulation of blood pressure, the epithelial sodium channel (ENaC), and other key renal sodium transporters by chronic insulin infusion in rats

2006 ◽  
Vol 290 (5) ◽  
pp. F1055-F1064 ◽  
Author(s):  
Jian Song ◽  
Xinqun Hu ◽  
Shahla Riazi ◽  
Swasti Tiwari ◽  
James B. Wade ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Sodium Channel ◽  
Insulin Infusion ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Kidney Cortex ◽  
Sodium Reabsorption ◽  
Cortical Collecting Duct ◽  
Sprague Dawley ◽  
Epithelial Sodium Channel Enac

Hyperinsulinemia is associated with hypertension. Dysregulation of renal distal tubule sodium reabsorption may play a role. We evaluated the regulation of the epithelial sodium channel (ENaC) and the thiazide-sensitive Na-Cl cotransporter (NCC) during chronic hyperinsulinemia in rats and correlated these changes to blood pressure as determined by radiotelemetry. Male Sprague-Dawley rats (∼270 g) underwent one of the following three treatments for 4 wk ( n = 6/group): 1) control; 2) insulin-infused plus 20% dextrose in drinking water; or 3) glucose water-drinking (20% dextrose in water). Mean arterial pressures were increased by insulin and glucose (mmHg at 3 wk): 98 ± 1 (control), 107 ± 2 (insulin), and 109 ± 3 (glucose), P < 0.01. Insulin (but not glucose) increased natriuretic response to benzamil (ENaC inhibitor) and hydrochlorothiazide (NCC inhibitor) on average by 125 and 60%, respectively, relative to control rats, suggesting increased activity of these reabsorptive pathways. Neither insulin nor glucose affected the renal protein abundances of NCC or the ENaC subunits (α, β, and γ) in kidney cortex, outer medulla, or inner medulla in a major way, as determined by immunoblotting. However, insulin and to some extent glucose increased apical localization of these subunits in cortical collecting duct principal cells, as determined by immunoperoxidase labeling. In addition, insulin decreased cortical “with no lysine” kinase (WNK4) abundance (by 16% relative to control), which may have increased NCC activity. Overall, insulin infusion increased blood pressure, and NCC and ENaC activity in rats. Increased apical targeting of ENaC and decreased WNK4 expression may be involved.

scholarly journals Peroxisome proliferator-activated receptor-γ agonists repress epithelial sodium channel expression in the kidney

2012 ◽  
Vol 302 (5) ◽  
pp. F540-F551 ◽  
Author(s):  
Emily Borsting ◽  
Vicki Pei-Chun Cheng ◽  
Chris K. Glass ◽  
Volker Vallon ◽  
Robyn Cunard
Keyword(s):  
Protein Expression ◽  
Sodium Channel ◽  
Mrna Expression ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Duct Cell ◽  
Kidney Cortex ◽  
Peroxisome Proliferator ◽  
Cortical Collecting Duct ◽  
Peroxisome Proliferator Activated Receptor

Thiazolidinediones (TZDs), known as peroxisome proliferator-activated receptor (PPAR) agonists, are used to treat type 2 diabetes. However, ∼5% of patients experience the treatment-limiting side effect of edema. Studies have implicated activation of the epithelial sodium channel (ENaC) as a cause of TZD-induced fluid retention, although there have been conflicting reports. The goal of this study was to resolve the role of PPARγ in control of ENaC isoforms in the kidney. Herein, we demonstrate in mice that rosiglitazone (RGZ), a PPARγ ligand, increases body weight and abdominal fat pad fluid content and reduces hematocrit. Seven days of RGZ decreases ENaCα and ENaCβ mRNA and ENaCγ protein expression in the kidney cortex, and acute treatment for 5 h with pioglitazone, another potent TZD, does not increase renal ENaC isoform mRNA or protein expression. Pioglitazone also decreases ENaCα and ENaCγ mRNA expression in a cortical collecting duct cell line. As no direct transcriptional studies had been conducted, we examined the PPARγ-dependent regulation of ENaC. Pioglitazone represses ENaCγ promoter activity, and this repression is partially relieved by inhibition of protein synthesis. Chromatin immunoprecipitation assays revealed that repression is associated with a decrease in histone H4K5 acetylation at the proximal ENaCγ promoter. In summary, TZDs do not increase ENaC mRNA expression in the kidney, and in fact repress the ENaCγ promoter via an indirect transcriptional mechanism.

scholarly journals The Epithelial Sodium Channel (ENaC) Traffics to Apical Membrane in Lipid Rafts in Mouse Cortical Collecting Duct Cells

2007 ◽  
Vol 282 (52) ◽  
pp. 37402-37411 ◽  
Author(s):  
Warren G. Hill ◽  
Michael B. Butterworth ◽  
Huamin Wang ◽  
Robert S. Edinger ◽  
Jonathan Lebowitz ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Lipid Rafts ◽  
Apical Membrane ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Cortical Collecting Duct ◽  
Duct Cells ◽  
Collecting Duct Cells ◽  
Epithelial Sodium Channel Enac

scholarly journals Sub-chronic testosterone treatment increases the levels of epithelial sodium channel (ENaC)-α,βandγin the kidney of orchidectomized adult male Sprague–Dawley rats

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2145 ◽  
Author(s):  
Su Yi Loh ◽  
Nelli Giribabu ◽  
Naguib Salleh
Keyword(s):  
Blood Pressure ◽  
Sodium Channel ◽  
Adult Male ◽  
Epithelial Sodium Channel ◽  
Physiological Parameter ◽  
Mrna Levels ◽  
Sprague Dawley ◽  
Collecting Ducts ◽  
Distal Tubules ◽  
Epithelial Sodium Channel Enac

Testosterone has been reported to cause blood pressure to increase. However mechanisms that underlie the effect of this hormone on this physiological parameter are currently not well understood. The aims of this study were to investigate effects of testosterone on expression ofα,βandγ-epithelial sodium channel (ENaC) proteins and messenger RNAs (mRNAs) in kidneys, the channel known to be involved in Na+reabsorption, which subsequently can affect the blood pressure.Methods.Adult male Sprague–Dawley (SD) rats were orchidectomized fourteen days prior to receiving seven days treatment with testosterone propionate (125 µg/kg/day or 250 µg/kg/day) with or without flutamide (androgen receptor blocker) or finasteride (5α-reductase inhibitor). Following sacrifice, the kidneys were removed and were subjected forα,βandγ-ENaC protein and mRNA expression analyses by Western blotting and Real-time PCR (qPCR) respectively. The distribution ofα,βandγ-ENaC proteins in kidneys were observed by immunofluorescence.Results.Theα,βandγ-ENaC proteins and mRNA levels in kidneys were enhanced in rats which received testosterone-only treatment. In these rats,α,βandγ-ENaC proteins were distributed in the distal tubules and collecting ducts of the nephrons. Co-treatment with flutamide or finasteride resulted in the levels ofα,βandγ-ENaC proteins and mRNAs in kidneys to decrease. In conclusions, increases inα,βandγ-ENaC protein and mRNA levels in kidneys mainly in the distal tubules and collecting ducts under testosterone influence might lead to enhance Na+reabsorption which subsequently might cause an increase in blood pressure.

Aldosterone-dependent and -independent regulation of the epithelial sodium channel (ENaC) in mouse distal nephron

2012 ◽  
Vol 303 (9) ◽  
pp. F1289-F1299 ◽  
Author(s):  
Viatcheslav Nesterov ◽  
Anke Dahlmann ◽  
Bettina Krueger ◽  
Marko Bertog ◽  
Johannes Loffing ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Single Channel ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Salt Diet ◽  
Low Salt ◽  
Immunohistochemical Evidence ◽  
Epithelial Sodium Channel Enac

Aldosterone is thought to be the main hormone to stimulate the epithelial sodium channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN) comprising the late distal convoluted tubule (DCT2), the connecting tubule (CNT) and the entire collecting duct (CD). There is immunohistochemical evidence for an axial gradient of ENaC expression along the ASDN with highest expression in the DCT2 and CNT. However, most of our knowledge about renal ENaC function stems from studies in the cortical collecting duct (CCD). Here we investigated ENaC function in the transition zone of DCT2/CNT or CNT/CCD microdissected from mice maintained on different sodium diets to vary plasma aldosterone levels. Single-channel recordings demonstrated amiloride-sensitive Na+ channels in DCT2/CNT with biophysical properties typical for ENaC previously described in CNT/CCD. In animals maintained on a standard salt diet, the average ENaC-mediated whole cell current (Δ Iami) was higher in DCT2/CNT than in CNT/CCD. A low salt diet increased Δ Iami in CNT/CCD but had little effect on Δ Iami in DCT2/CNT. To investigate whether aldosterone is necessary for ENaC activity in the DCT2/CNT, we used aldosterone synthase knockout (AS−/−) mice that lack aldosterone. In CNT/CCD of AS−/− mice, Δ Iami was lower than that in wild-type (WT) animals and was not stimulated by a low salt diet. In contrast, in DCT2/CNT of AS−/− mice, Δ Iami was similar to that in DCT2/CNT of WT animals both on a standard and on a low salt diet. We conclude that ENaC function in the DCT2/CNT is largely independent of aldosterone which is in contrast to its known aldosterone sensitivity in CNT/CCD.

Localization of epithelial sodium channel and aquaporin-2 in rabbit kidney cortex

2000 ◽  
Vol 278 (4) ◽  
pp. F530-F539 ◽  
Author(s):  
Johannes Loffing ◽  
Dominique Loffing-Cueni ◽  
Andreas Macher ◽  
Steven C. Hebert ◽  
Beatriz Olson ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Collecting Duct ◽  
Water Channel ◽  
Distribution Patterns ◽  
Epithelial Sodium Channel ◽  
Transport Systems ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Cortical Collecting Duct ◽  
Aquaporin 2

The amiloride-sensitive epithelial sodium channel (ENaC) and the vasopressin-dependent water channel aquaporin-2 (AQP2) mediate mineralocorticoid-regulated sodium- and vasopressin-regulated water reabsorption, respectively. Distributions of ENaC and AQP2 have been shown by immunohistochemistry in rats. Functional data from rabbits suggest a different distribution pattern of these channels than in rats. We studied, by immunohistochemistry in the rabbit kidney cortex, the distributions of ENaC and AQP2, in conjunction with marker proteins for distal segments. In rabbit cortex ENaC is restricted to the connecting tubule (CNT) cells and cortical collecting duct (CCD) cells. The intracellular distribution of ENaC shifts from the apical membrane in the most upstream CNT cells to a cytoplasmic location further downstream in the CNT and in the CCD cells. AQP2 is detected in the CCD cells exclusively. The anatomic subdivisions in the rabbit distal nephron coincide exactly with distributions of apical transport systems. The differences between rabbits and rats in the distribution patterns of ENaC and AQP2 may explain functional differences in renal salt and water handling between these species.

scholarly journals Conditional Transgenic Mice for Studying the Role of the Glucocorticoid Receptor in the Renal Collecting Duct

Endocrinology ◽  
2008 ◽  
Vol 150 (5) ◽  
pp. 2202-2210 ◽  
Author(s):  
Aurélie Nguyen Dinh Cat ◽  
Antoine Ouvrard-Pascaud ◽  
François Tronche ◽  
Maud Clemessy ◽  
Daniel Gonzalez-Nunez ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Glucocorticoid Receptor ◽  
Sodium Channel ◽  
Leucine Zipper ◽  
Collecting Duct ◽  
Extracellular Volume ◽  
Epithelial Sodium Channel ◽  
Sodium Reabsorption ◽  
Renal Collecting Duct

The mineralocorticoid receptor (MR) is a major regulator of renal sodium reabsorption and body fluid homeostasis. However, little is known about glucocorticoid receptor (GR)-dependent renal effects. Glucocorticoids may activate both receptors, so it is difficult to distinguish between MR- and GR-mediated effects in vivo. To overcome this complexity, we used a transgenic mouse model allowing conditional GR overexpression (doxycycline inducible TetON system, Hoxb7 promoter) in the renal collecting duct (CD) to identify GR-regulated genes involved in sodium transport in the CD. In microdissected cortical CD, induction of GR expression led (after 2 d of doxycycline) to increased α-epithelial sodium channel and glucocorticoid-induced leucine zipper and decreased abundance of with-no-lysine kinase 4 transcripts, without modification of Na,K-ATPase, serum- and glucocorticoid-kinase-1, or MR expression. No changes occurred in the upstream distal and connecting tubules [distal convoluted tubule (DCT), connecting tubule (CNT)]. Sodium excretion was unaltered, but the urinary aldosterone concentration was reduced, suggesting compensation of transitory extracellular volume expansion that subsequently disappeared. At steady state, i.e. after 15 d of doxycycline administration, transcript abundance remained altered in the CD, whereas mirror changes appeared in the DCT and CNT. Plasma aldosterone or glucocorticoids and blood pressure were all unaffected. These experiments show that: 1) GR, in addition to MR, controls epithelial sodium channel- and glucocorticoid-induced leucine zipper expression in vivo in the CD; 2) with-no-lysine kinase 4 is negatively controlled by GR; and 3) the DCT and CNT compensate for these alterations to maintain normal sodium reabsorption and blood pressure. These results suggest that enhanced GR expression may contribute to enhanced sodium retention in some pathological situations.

scholarly journals Rab11b regulates the trafficking and recycling of the epithelial sodium channel (ENaC)

2012 ◽  
Vol 302 (5) ◽  
pp. F581-F590 ◽  
Author(s):  
Michael B. Butterworth ◽  
Robert S. Edinger ◽  
Mark R. Silvis ◽  
Luciana I. Gallo ◽  
Xiubin Liang ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Collecting Duct ◽  
Fluorescent Microscopy ◽  
Epithelial Sodium Channel ◽  
Surface Expression ◽  
Small Gtpases ◽  
Dominant Negative ◽  
Cortical Collecting Duct ◽  
Interfering Rna ◽  
Epithelial Sodium Channel Enac

Expression of the epithelial sodium channel (ENaC) at the apical membrane of cortical collecting duct (CCD) principal cells is modulated by regulated trafficking mediated by vesicle insertion and retrieval. Small GTPases are known to facilitate vesicle trafficking, recycling, and membrane fusion events; however, little is known about the specific Rab family members that modify ENaC surface density. Using a mouse CCD cell line that endogenously expresses ENaC (mpkCCD), the channel was localized to both Rab11a- and Rab11b-positive endosomes by immunoisolation and confocal fluorescent microscopy. Expression of a dominant negative (DN) form of Rab11a or Rab11b significantly reduced the basal and cAMP-stimulated ENaC-dependent sodium (Na+) transport. The greatest reduction in Na+ transport was observed with the expression of DN-Rab11b. Furthermore, small interfering RNA-mediated knockdown of each Rab11 isoform demonstrated the requirement for Rab11b in ENaC surface expression. These data indicate that Rab11b, and to a lesser extent Rab11a, is involved in establishing the constitutive and cAMP-stimulated Na+ transport in mpkCCD cells.

scholarly journals Prostaglandin E2 stimulates the epithelial sodium channel (ENaC) in cultured mouse cortical collecting duct cells in an autocrine manner

2020 ◽  
Vol 152 (8) ◽  
Author(s):  
Morag K. Mansley ◽  
Christian Niklas ◽  
Regina Nacken ◽  
Kathrin Mandery ◽  
Hartmut Glaeser ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Sodium Channel ◽  
Sodium Transport ◽  
Collecting Duct ◽  
Epithelial Sodium Channel ◽  
Prostaglandin E ◽  
Cortical Collecting Duct ◽  
Transepithelial Sodium Transport ◽  
Epithelial Sodium Channel Enac

Prostaglandin E2 (PGE2) is the most abundant prostanoid in the kidney, affecting a wide range of renal functions. Conflicting data have been reported regarding the effects of PGE2 on tubular water and ion transport. The amiloride-sensitive epithelial sodium channel (ENaC) is rate limiting for transepithelial sodium transport in the aldosterone-sensitive distal nephron. The aim of the present study was to explore a potential role of PGE2 in regulating ENaC in cortical collecting duct (CCD) cells. Short-circuit current (ISC) measurements were performed using the murine mCCDcl1 cell line known to express characteristic properties of CCD principal cells and to be responsive to physiological concentrations of aldosterone and vasopressin. PGE2 stimulated amiloride-sensitive ISC via basolateral prostaglandin E receptors type 4 (EP4) with an EC50 of ∼7.1 nM. The rapid stimulatory effect of PGE2 on ISC resembled that of vasopressin. A maximum response was reached within minutes, coinciding with an increased abundance of β-ENaC at the apical plasma membrane and elevated cytosolic cAMP levels. The effects of PGE2 and vasopressin were nonadditive, indicating similar signaling cascades. Exposing mCCDcl1 cells to aldosterone caused a much slower (∼2 h) increase of the amiloride-sensitive ISC. Interestingly, the rapid effect of PGE2 was preserved even after aldosterone stimulation. Furthermore, application of arachidonic acid also increased the amiloride-sensitive ISC involving basolateral EP4 receptors. Exposure to arachidonic acid resulted in elevated PGE2 in the basolateral medium in a cyclooxygenase 1 (COX-1)–dependent manner. These data suggest that in the cortical collecting duct, locally produced and secreted PGE2 can stimulate ENaC-mediated transepithelial sodium transport.

Sign in / Sign up

Export Citation Format

Share Document