Increased CO2 stimulates K/Rb reabsorption mediated by H-K-ATPase in CCD of potassium-restricted rabbit

2001 ◽  
Vol 281 (2) ◽  
pp. F366-F373 ◽  
Author(s):  
Xiaoming Zhou ◽  
Suguru Nakamura ◽  
Shen-Ling Xia ◽  
Charles S. Wingo
Keyword(s):  
Intracellular Calcium ◽  
Collecting Duct ◽  
Apical Plasma Membrane ◽  
Cortical Collecting Duct ◽  
Intracellular Acidosis ◽  
Simultaneous Exposure ◽  
Time Control ◽  
Absorptive Flux ◽  
Stimulation Of

Apical H-K-ATPase in the cortical collecting duct (CCD) plays an important role in urinary acidification and K reabsorption. Our previous studies demonstrated that an H-K-ATPase mediates, in part, Rb reabsorption in rabbit CCD (Zhou X and Wingo CS. Am J Physiol Renal Fluid Electrolyte Physiol 263: F1134–F1141, 1992). The purpose of these experiments was to examine using in vitro microperfused CCD from K-restricted rabbits 1) whether an acute increase in Pco 2 and, presumably, intracellular acidosis stimulate K absorptive flux; and 2) whether this stimulation was dependent on the presence of a functional H-K-ATPase. Rb reabsorption was significantly increased after exposure to 10% CO2 in CCD, and this effect was persistent for the entire 10% CO2 period, whereas 10 μM SCH-28080 in the perfusate totally abolished the stimulation of Rb reabsorption by 10% CO2. After stimulation of Rb reabsorption by 10% CO2, subsequent addition of 0.1 mM methazolamide, an inhibitor of carbonic anhydrase, failed to affect Rb reabsorption. However, simultaneous exposure to 10% CO2 and methazolamide prevented the stimulation of Rb reabsorption. Treatment with the intracellular calcium chelator MAPTAM (0.5 μM) inhibited the stimulation of Rb reabsorption by 10% CO2. Similar inhibition was also observed in the presence of either a calmodulin inhibitor, W-7 (0.5 μM), or colchicine (0.5 mM), an inhibitor of tubulin polymerization. In time control studies, the perfusion time did not significantly affect Rb reabsorption. We conclude the following: 1) stimulation of Rb reabsorption on exposure to 10% CO2 is dependent on the presence of a functional H-K-ATPase and appears to be regulated in part by the insertion of this enzyme into the apical plasma membrane by exocytosis; 2) insertion of H-K-ATPase requires changes in intracellular pH and needs a basal level of intracellular calcium concentration; and 3) H-K-ATPase insertion occurs by a microtubule-dependent process.

Stimulation of total CO2 flux by 10% CO2 in rabbit CCD: role of an apical Sch-28080- and Ba-sensitive mechanism

1994 ◽  
Vol 267 (1) ◽  
pp. F114-F120 ◽  
Author(s):  
X. Zhou ◽  
C. S. Wingo
Keyword(s):  
Collecting Duct ◽  
Co2 Flux ◽  
K Channel ◽  
Co2 Absorption ◽  
Cortical Collecting Duct ◽  
Atpase Inhibitor ◽  
Contrast Exposure ◽  
Stimulation Of

These studies examine the effect of ambient PCO2 on net bicarbonate (total CO2) absorption by the in vitro perfused cortical collecting duct (CCD) from K-replete rabbits and the mechanism responsible for this effect. Exposure to 10% CO2 increased net bicarbonate flux (total CO2 flux, JtCO2) by 1.8-fold (P < 0.005), and this effect was inhibited by luminal 10 microM Sch-28080, an H-K-adenosinetriphosphatase (H-K-ATPase) inhibitor. In contrast, exposure to 10% CO2 significantly decreased Rb efflux, and this decrement in Rb efflux was blocked by luminal 2 mM Ba, a K channel blocker. Thus transepithelial tracer Rb flux did not increase upon exposure to 10% CO2 as we have observed in this segment under K-restricted conditions. The observation that 10% CO2 increased net bicarbonate absorption without a change in absorptive Rb flux suggested that 10% CO2 increased apical K recycling. To test this hypothesis, we examined whether luminal Ba inhibited the stimulation of luminal acidification induced by 10% CO2. If apical K exit were necessary for full activation of proton secretion, then inhibiting K exit should indirectly affect the stimulation of JtCO2 by 10% CO2. In fact, the effect of 10% CO2 on JtCO2 in the presence of 2 mM luminal Ba was quantitatively indistinguishable from the effect of 10% CO2 on JtCO2 in the presence of 10 microM luminal Sch-28080.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphate transport by isolated rabbit cortical collecting tubule

1980 ◽  
Vol 238 (5) ◽  
pp. F358-F362
Author(s):  
R. A. Peraino ◽  
W. N. Suki
Keyword(s):  
Specific Activity ◽  
Collecting Duct ◽  
Phosphate Transport ◽  
Cortical Collecting Duct ◽  
Renal Handling ◽  
Bathing Medium ◽  
Collecting Tubule ◽  
Absorptive Flux ◽  
Cortical Collecting Tubule

Renal handling of phosphate occurs in the proximal convoluted tubule. Absorption of this anion also occurs in the pars recta and distal convoluted tubule, the latter a structurally and functionally diverse segment. The purpose of the present investigation was to examine phosphate transport by the cortical collecting duct of the rabbit. Segments of cortical collecting tubule, beyond the last cortical branch, were isolated and perfused in vitro with an artificial solution simulating plasma as the perfusing and bathing medium. The perfusion solution contained either 3 or 25 mM bicarbonate. Net phosphate transport was measured using 32P as the radionuclide tracer, with identical specific activity in perfusing and bathing solutions. A net absorptive flux for phosphate was demonstrated, amounting to 2-3% of the delivered load. In addition, this absorptive flux was linearly related to perfusion rate and, thus, delivered load, but independent of the lumen bicarbonate concentration or pH.

scholarly journals Effects of ammonia on bicarbonate transport in the cortical collecting duct

2000 ◽  
Vol 278 (2) ◽  
pp. F219-F226 ◽  
Author(s):  
Amy E. Frank ◽  
Charles S. Wingo ◽  
I. David Weiner
Keyword(s):  
Collecting Duct ◽  
Potassium Transport ◽  
Bicarbonate Transport ◽  
Cortical Collecting Duct ◽  
Intracellular Acidification ◽  
Bicarbonate Reabsorption ◽  
Atpase Inhibitors ◽  
Collecting Ducts ◽  
Stimulation Of

Both acidosis and hypokalemia stimulate renal ammoniagenesis, and both regulate urinary proton and potassium excretion. We hypothesized that ammonia might play an important role in this processing by stimulating H+-K+-ATPase-mediated ion transport. Rabbit cortical collecting ducts (CCD) were studied using in vitro microperfusion, bicarbonate reabsorption was measured using microcalorimetry, and intracellular pH (pHi) was measured using the fluorescent, pH-sensitive dye, 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Ammonia caused a concentration-dependent increase in net bicarbonate reabsorption that was inhibited by luminal addition of either of the H+-K+-ATPase inhibitors, Sch-28080 or ouabain. The stimulation of net bicarbonate reabsorption was not mediated through apical H+-ATPase, basolateral Na+-K+-ATPase, or luminal electronegativity. Although ammonia caused intracellular acidification, similar changes in pHi induced by inhibiting basolateral Na+/H+ exchange did not alter net bicarbonate reabsorption. We conclude that ammonia regulates CCD proton and potassium transport, at least in part, by stimulating apical H+-K+-ATPase.

scholarly journals Mechanisms through which ammonia regulates cortical collecting duct net proton secretion

2002 ◽  
Vol 282 (6) ◽  
pp. F1120-F1128 ◽  
Author(s):  
Amy E. Frank ◽  
Charles S. Wingo ◽  
Peter M. Andrews ◽  
Shana Ageloff ◽  
Mark A. Knepper ◽  
...  
Keyword(s):  
Intracellular Calcium ◽  
Tetanus Toxin ◽  
Collecting Duct ◽  
Vesicle Fusion ◽  
Snare Proteins ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Bicarbonate Reabsorption ◽  
Subapical Region ◽  
Stimulation Of

Ammonia stimulates cortical collecting duct (CCD) net bicarbonate reabsorption by activating an apical H+-K+-ATPase through mechanisms that are independent of ammonia's known effects on intracellular pH and active sodium transport. The present studies examined whether this stimulation occurs through soluble N-ethylmaleimide-sensitive fusion attachment receptor (SNARE) protein-mediated vesicle fusion. Rabbit CCD segments were studied using in vitro microperfusion, and transepithelial bicarbonate transport was measured using microcalorimetry. Ammonia's stimulation of bicarbonate reabsorption was blocked by either chelating intracellular calcium with 1,2-bis(2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid acetoxymethyl ester or by inhibiting microtubule polymerization with colchicine compared with parallel studies performed in the absence of these inhibitors. An inactive structural analog of colchicine, lumicolchicine, did not alter ammonia's stimulation of bicarbonate reabsorption. Tetanus toxin, a zinc endopeptidase specific for vesicle-associated SNARE (v-SNARE) proteins, prevented ammonia from stimulating net bicarbonate reabsorption. Consistent with the functional evidence for v-SNARE involvement, antibodies directed against a conserved region of isoforms 1–3 of the tetanus toxin-sensitive, vesicle-associated membrane protein (VAMP) members of v-SNARE proteins labeled the apical and subapical region of collecting duct intercalated cells. Similarly, antibodies to NSF protein, a protein involved in activation of SNARE proteins for subsequent vesicle fusion, localized to the apical and subapical region of collecting duct intercalated cells. These results indicate that ammonia stimulates CCD bicarbonate reabsorption through an intracellular calcium-dependent, microtubule-dependent, and v-SNARE-dependent mechanism that appears to involve insertion of cytoplasmic vesicles into the apical plasma membrane of CCD intercalated cells.

Regulation of pendrin by cAMP: possible involvement in β-adrenergic-dependent NaCl retention

2012 ◽  
Vol 302 (9) ◽  
pp. F1180-F1187 ◽  
Author(s):  
Anie Azroyan ◽  
Luciana Morla ◽  
Gilles Crambert ◽  
Kamel Laghmani ◽  
Sureshkrishna Ramakrishnan ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Collecting Duct ◽  
Cortical Collecting Duct ◽  
Membrane Expression ◽  
Opossum Kidney ◽  
Pka Pathway ◽  
Β Adrenergic Receptors ◽  
Renal Sympathetic ◽  
Stimulation Of

The sodium-independent anion exchanger pendrin is expressed in several tissues including the kidney cortical collecting duct (CCD), where it acts as a chloride/bicarbonate exchanger and has been shown to participate in the regulation of acid-base homeostasis and blood pressure. The renal sympathetic nervous system is known to play a key role in the development of salt-induced hypertension. This study aimed to determine whether pendrin may partly mediate the effects of β adrenergic receptors (β-AR) on renal salt handling. We investigated the regulation of pendrin activity by the cAMP/protein kinase A (PKA) signaling pathway, both in vitro in opossum kidney proximal (OKP) cells stably transfected with pendrin cDNA and ex vivo in isolated microperfused CCDs stimulated by isoproterenol, a β-AR agonist. We found that stimulation of the cAMP/PKA pathway in OKP cells increased the amount of pendrin at the cell surface as well as its transport activity. These effects stemmed from increased exocytosis of pendrin and were associated with its phosphorylation. Furthermore, cAMP effects on the membrane expression and activity of pendrin were abolished by mutating the serine 49 located in the intracellular N-terminal domain of pendrin. Finally, we showed that isoproterenol increases pendrin trafficking to the apical membrane as well as the reabsorption of both Cl− and Na+ in microperfused CCDs. All together, our results strongly suggest that pendrin activation by the cAMP/PKA pathway underlies isoproterenol-induced stimulation of NaCl reabsorption in the kidney collecting duct, a mechanism likely involved in the sodium-retaining effect of β-adrenergic agonists.

scholarly journals The Role of Intercalated Cell Nedd4–2 in BP Regulation, Ion Transport, and Transporter Expression

2018 ◽  
Vol 29 (6) ◽  
pp. 1706-1719 ◽  
Author(s):  
Masayoshi Nanami ◽  
Truyen D. Pham ◽  
Young Hee Kim ◽  
Baoli Yang ◽  
Roy L. Sutliff ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Collecting Duct ◽  
Transepithelial Transport ◽  
Apical Plasma Membrane ◽  
Cortical Collecting Duct ◽  
Ubiquitin Protein Ligase ◽  
Intercalated Cell ◽  
Gene Ablation ◽  
And Function

BackgroundNedd4–2 is an E3 ubiquitin-protein ligase that associates with transport proteins, causing their ubiquitylation, and then internalization and degradation. Previous research has suggested a correlation between Nedd4–2 and BP. In this study, we explored the effect of intercalated cell (IC) Nedd4–2 gene ablation on IC transporter abundance and function and on BP.Methods We generated IC Nedd4–2 knockout mice using Cre-lox technology and produced global pendrin/Nedd4–2 null mice by breeding global Nedd4–2 null (Nedd4–2−/−) mice with global pendrin null (Slc26a4−/−) mice. Mice ate a diet with 1%–4% NaCl; BP was measured by tail cuff and radiotelemetry. We measured transepithelial transport of Cl− and total CO2 and transepithelial voltage in cortical collecting ducts perfused in vitro. Transporter abundance was detected with immunoblots, immunohistochemistry, and immunogold cytochemistry.Results IC Nedd4–2 gene ablation markedly increased electroneutral Cl−/HCO3− exchange in the cortical collecting duct, although benzamil-, thiazide-, and bafilomycin-sensitive ion flux changed very little. IC Nedd4–2 gene ablation did not increase the abundance of type B IC transporters, such as AE4 (Slc4a9), H+-ATPase, barttin, or the Na+-dependent Cl−/HCO3− exchanger (Slc4a8). However, IC Nedd4–2 gene ablation increased CIC-5 total protein abundance, apical plasma membrane pendrin abundance, and the ratio of pendrin expression on the apical membrane to the cytoplasm. IC Nedd4–2 gene ablation increased BP by approximately 10 mm Hg. Moreover, pendrin gene ablation eliminated the increase in BP observed in global Nedd4–2 knockout mice.Conclusions IC Nedd4–2 regulates Cl−/HCO3− exchange in ICs., Nedd4–2 gene ablation increases BP in part through its action in these cells.

scholarly journals Nitric oxide reduces Cl− absorption in the mouse cortical collecting duct through an ENaC-dependent mechanism

2013 ◽  
Vol 304 (11) ◽  
pp. F1390-F1397 ◽  
Author(s):  
Vladimir Pech ◽  
Monika Thumova ◽  
Sergey I. Dikalov ◽  
Edith Hummler ◽  
Bernard C. Rossier ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Angiotensin Ii ◽  
Collecting Duct ◽  
No Synthase ◽  
Apical Plasma Membrane ◽  
No Production ◽  
Cortical Collecting Duct ◽  
No Donor ◽  
Genetic Ablation

Since nitric oxide (NO) participates in the renal regulation of blood pressure, in part, by modulating transport of Na+ and Cl− in the kidney, we asked whether NO regulates net Cl− flux ( JCl) in the cortical collecting duct (CCD) and determined the transporter(s) that mediate NO-sensitive Cl− absorption. Cl− absorption was measured in CCDs perfused in vitro that were taken from aldosterone-treated mice. Administration of an NO donor (10 μM MAHMA NONOate) reduced JCl and transepithelial voltage ( VT) both in the presence or absence of angiotensin II. However, reducing endogenous NO production by inhibiting NO synthase (100 μM NG-nitro-l-arginine methyl ester) increased JCl only in the presence of angiotensin II, suggesting that angiotensin II stimulates NO synthase activity. To determine the transport process that mediates NO-sensitive changes in JCl, we examined the effect of NO on JCl following either genetic ablation or chemical inhibition of transporters in the CCD. Since the application of hydrochlorothiazide (100 μM) or bafilomycin (5 nM) to the perfusate or ablation of the gene encoding pendrin did not alter NO-sensitive JCl, NO modulates JCl independent of the Na+-dependent Cl−/HCO3− exchanger (NDCBE, Slc4a8), the A cell apical plasma membrane H+-ATPase and pendrin. In contrast, both total and NO-sensitive JCl and VT were abolished with application of an epithelial Na+ channel (ENaC) inhibitor (3 μM benzamil) to the perfusate. We conclude that NO reduces Cl− absorption in the CCD through a mechanism that is ENaC-dependent.

DA1 dopamine receptors in renal cortical collecting duct

1991 ◽  
Vol 261 (5) ◽  
pp. F890-F895 ◽  
Author(s):  
K. Ohbu ◽  
R. A. Felder
Keyword(s):  
Adenylate Cyclase ◽  
Specific Binding ◽  
Collecting Duct ◽  
Sch 23390 ◽  
Receptor Density ◽  
Cortical Collecting Duct ◽  
Tightly Coupled ◽  
Renal Dopamine ◽  
Dissociation Constant Kd ◽  
Stimulation Of

Renal dopamine DA1 receptors are linked to the regulation of sodium transport. We have previously reported the presence of DA1 receptors in the proximal convoluted tubule (PCT) but not in the distal convoluted tubule. However, the DA1 receptor in the collecting duct, the final determinant of electrolyte transport, has not been studied. DA1 receptors were studied in the microdissected cortical collecting duct (CCD) of rats by autoradiography with use of the selective DA1 radioligand 125I-Sch 23982 and by measurement of adenylate cyclase (AC) activity. Specific binding of 125I-Sch 23982 to CCD was saturable with radioligand concentration. The dissociation constant (Kd) was 0.46 +/- 0.08 nM (n = 5), and the maximum receptor density (Bmax) was 1.41 +/- 0.43 fmol/mg protein (n = 5). The DA1 antagonist Sch 23390 was more effective than the DA1 agonist fenoldopam in competing for specific 125I-Sch 23982 binding. Fenoldopam stimulated AC activity in CCD in a concentration-dependent (10(-9)-10(-6) M) manner. The ability of fenoldopam to stimulate AC activity was similar in CCD and PCT even though DA1 receptor density was 1,000 times greater in the CCD than in the PCT. In additional studies, fenoldopam stimulation of AC activity did not influence vasopressin-stimulated AC activity. We conclude that the DA1 receptor in rat CCD is tightly coupled to AC stimulation and that there is no interaction between DA1 agonist-stimulated and vasopressin-stimulated AC activity in the CCD.

scholarly journals Role of NKCC in BK channel-mediated net K+ secretion in the CCD

2011 ◽  
Vol 301 (5) ◽  
pp. F1088-F1097 ◽  
Author(s):  
Wen Liu ◽  
Carlos Schreck ◽  
Richard A. Coleman ◽  
James B. Wade ◽  
Yubelka Hernandez ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Bk Channels ◽  
Bk Channel ◽  
Taqman Assay ◽  
Specific Cell ◽  
Cortical Collecting Duct ◽  
Ph Indicator ◽  
Transport Pathway ◽  
K Secretion

Apical SK/ROMK and BK channels mediate baseline and flow-induced K secretion (FIKS), respectively, in the cortical collecting duct (CCD). BK channels are detected in acid-base transporting intercalated (IC) and Na-absorbing principal (PC) cells. Although the density of BK channels is greater in IC than PC, Na-K-ATPase activity in IC is considered inadequate to sustain high rates of urinary K secretion. To test the hypothesis that basolateral NKCC in the CCD contributes to BK channel-mediated FIKS, we measured net K secretion ( JK) and Na absorption ( JNa) at slow (∼1) and fast (∼5 nl·min−1·mm−1) flow rates in rabbit CCDs microperfused in vitro in the absence and presence of bumetanide, an inhibitor of NKCC, added to the bath. Bumetanide inhibited FIKS but not basal JK, JNa, or the flow-induced [Ca2+]i transient necessary for BK channel activation. Addition of luminal iberiotoxin, a BK channel inhibitor, to bumetanide-treated CCDs did not further reduce JK. Basolateral Cl removal reversibly inhibited FIKS but not basal JK or JNa. Quantitative PCR performed on single CCD samples using NKCC1- and 18S-specific primers and probes and the TaqMan assay confirmed the presence of the transcript in this nephron segment. To identify the specific cell type to which basolateral NKCC is localized, we exploited the ability of NKCC to accept NH4+ at its K-binding site to monitor the rate of bumetanide-sensitive cytosolic acidification after NH4+ addition to the bath in CCDs loaded with the pH indicator dye BCECF. Both IC and PC were found to have a basolateral bumetanide-sensitive NH4+ entry step and NKCC1-specific antibodies labeled the basolateral surfaces of both cell types in CCDs. These results suggest that BK channel-mediated FIKS is dependent on a basolateral bumetanide-sensitive, Cl-dependent transport pathway, proposed to be NKCC1, in both IC and PC in the CCD.

EGF promotes gastric mucosal restitution by activating Na+/H+exchange of epithelial cells

2002 ◽  
Vol 282 (5) ◽  
pp. G866-G876 ◽  
Author(s):  
Akinori Yanaka ◽  
Hideo Suzuki ◽  
Takeshi Shibahara ◽  
Hirofumi Matsui ◽  
Akira Nakahara ◽  
...  
Keyword(s):  
Electrical Resistance ◽  
Egf Receptor ◽  
Mucous Cells ◽  
Egf Receptors ◽  
Intracellular Acidosis ◽  
Receptor Antibody ◽  
Epidermal Growth ◽  
Triton X ◽  
Stimulation Of

This study was conducted to determine whether the contributions of epidermal growth factor (EGF) to gastric mucosal restitution after injury are mediated by stimulation of Na+/H+exchangers in surface mucous cells (SMC). Intact sheets of guinea pig gastric mucosae were incubated in vitro. Intracellular pH (pHi) in SMC was measured fluorometrically, using 2′,7′- bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein. Restitution after Triton X-100-induced injury was evaluated by recovery of electrical resistance. At neutral luminal pH, exogenous EGF (ex-EGF) increased pHiand enhanced restitution in the absence but not in the presence of serosal HCO[Formula: see text]. During exposure to luminal acid, ex-EGF not only prevented intracellular acidosis but also promoted restitution. These effects of ex-EGF were blocked by serosal amiloride or anti-EGF-receptor antibody. In the absence of ex-EGF, restitution was inhibited by replacement of luminal and serosal solutions with fresh solutions and was blocked more completely by serosal anti-EGF-receptor antibody. These results suggest that both endogenous and ex-EGF contribute to restitution via basolateral EGF receptors, with effects mediated, at least in part, by stimulation of basolateral Na+/H+exchangers.

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