Stimulation of Cl- self exchange by intracellular HCO3- in rabbit cortical collecting duct

1989 ◽  
Vol 257 (1) ◽  
pp. C94-C101 ◽  
Author(s):  
K. Matsuzaki ◽  
J. B. Stokes ◽  
V. L. Schuster
Keyword(s):  
Anion Exchange ◽  
Intracellular Ph ◽  
Rate Coefficient ◽  
Collecting Duct ◽  
Cortical Collecting Duct ◽  
High K ◽  
Shift Experiment ◽  
Ethanesulfonic Acid ◽  
The Individual ◽  
Stimulation Of

In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, KCl (nm/s); a small fraction is effected by Cl--HCO3- exchange and Cl- diffusion. We previously reported that changing from a CO2-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) bath to a 5% CO2-25 mM HCO3- bath stimulates Cl- self exchange. Here, we examine in further detail the individual components of the CO2-HCO3- system that stimulate KCl. Addition of 0.5% CO2 to a HEPES bath (final pH = 7.24) stimulated KCl by 70 +/- 19 nm/s, a delta KCl comparable to that induced by 1% CO2 (pH 7.12), 6% CO2 (pH 6.6), or 6% CO2-25 mM HCO3- (pH 7.4). The roles of intracellular pH (pHi) and HCO3- concentration were examined by clamping pHi using high K+ and nigericin. Increasing pHi from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased KCl by 71 +/- 17 nm/s. These results suggest that pHi might regulate anion exchange. However, during such a pHi-shift experiment, metabolically derived CO2 produces a concomitant change in intracellular HCO3- concentration [( HCO3-]i). To determine whether an increase in [HCO3-]i could stimulate Cl- self exchange, we replaced HEPES with 6% CO2-5 mM HCO3- isohydrically (pHi clamped at 6.9). With this increase in [HCO3-]i at constant pHi, KCl increased by 51 +/- 10 nm/s. These maneuvers had negligible effects on Cl- diffusion and Cl--HCO3- exchange. These experiments demonstrate that increases in cell [HCO3-] (or perhaps CO2) can stimulate transepithelial anion exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Absence of transepithelial anion exchange by rabbit OMCD: evidence against reversal of cell polarity

1988 ◽  
Vol 255 (2) ◽  
pp. F220-F228 ◽  
Author(s):  
M. Hayashi ◽  
V. L. Schuster ◽  
J. B. Stokes
Keyword(s):  
Anion Exchange ◽  
Cell Polarity ◽  
Rate Coefficient ◽  
Collecting Duct ◽  
Ringer Solution ◽  
Base Line ◽  
Cortical Collecting Duct ◽  
Exchange System ◽  
Outer Medulla ◽  
Medullary Collecting Duct

In the rabbit cortical collecting duct (CCD), Cl tracer crosses the epithelium predominantly via an anion exchange system that operates in either a Cl-Cl or Cl-HCO3 exchange mode. In the present study, we used the 36Cl lumen-to-bath rate coefficient (KCl, nm/s), a sensitive measurement of CCD transepithelial anion transport, to investigate the nature of Cl transport in the medullary collecting duct dissected from inner stripe, outer medulla (OMCD). The KCl in OMCD perfused and bathed in HCO3-Ringer solution was low (46.2 +/- 8.5 nm/s) and similar to that value observed in the CCD when anion exchange is inhibited and Cl permeates the epithelium by diffusion. Unlike KCl in CCD, KCl in OMCD was not stimulated by adenosine 3',5'-cyclic monophosphate (cAMP). OMCD KCl was not altered by bath Cl and/or HCO3 removal, demonstrating the absence of transepithelial Cl-Cl and Cl-HCO3 exchange. To test the hypothesis that metabolic alkalosis could reverse the polarity of intercalated cells and thus induce an apical Cl-HCO3 exchanger in H+-secreting OMCD cells, we measured KCl in OMCD from rabbits made alkalotic by deoxycorticosterone and furosemide. Although the base-line KCl was slightly higher than in OMCD from control rabbits, the value was still far lower than the KCl under comparable conditions in CCD. Moreover, KCl in OMCD from alkalotic rabbits was unchanged by cAMP, or by sequential removal of bath HCO3 and Cl. Immunocytochemistry using peanut lectin and a monoclonal antibody to-erythrocyte band 3 failed to reveal any evidence for alkalosis-induced reversal of either CCD or OMCD intercalated cell polarity.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracellular pH dependence of buffer capacity and anion exchange in the parietal cell

1989 ◽  
Vol 257 (5) ◽  
pp. G741-G747 ◽  
Author(s):  
E. Wenzl ◽  
T. E. Machen
Keyword(s):  
Anion Exchange ◽  
Intracellular Ph ◽  
Anion Exchanger ◽  
Buffer Capacity ◽  
Ph Dependence ◽  
Disulfonic Acid ◽  
Rates Of Change ◽  
Ethanesulfonic Acid ◽  
Increased Activity ◽  
Stimulation Of

When parietal cells (PC) are stimulated with histamine, the anion exchanger rate increases three to five times to compensate for alkaline loading induced by H+-K+ adenosinetriphosphatase (ATPase) and to provide Cl for acid secretion. It has been hypothesized that this increased activity is caused by the increase in intracellular pH (pHi) that often occurs in stimulated PC (from 7.1 to a maximum of 7.3). The dependence of the anion exchanger on pHi was studied using microspectrofluorimetry of the pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF). N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered solutions were used because the anion exchanger can transport OH- (or HCO3) in exchange for Cl- even with [HCO3]o = 200 microM. It was found that when solutions were changed either from NaCl to Cl- free or Cl- free to NaCl, rates of change of pHi (delta pH/delta t) were strongly dependent on pHi: nearly 0 at pHi 6.6 and 1.25 pH/min at pHi 8.0. To convert these pHi changes into anion flux rates, the intrinsic buffer capacity (beta i) was determined over the same pHi range by making small changes of [NH4]o to determine the resulting changes of [NH4]i and pHi (i.e., beta i = delta[NH4]i/delta pHi) in PC that had been pretreated with 1 mM amiloride and 200 microM [H2]4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) [to block Na+-H+ and Cl- -OH-(HCO3-) exchange]. beta i was also strongly dependent on pHi: at pHi 6.5 beta i = 48 mM/pH, and this decreased as pHi increased; at pHi 7.75 beta i = 8 mM/pH. The derived anion fluxes (i.e., JOH = beta i x delta pH/delta t) were roughly linearly related to pHi between 6.6 (JOH near 0) and 8.1 (JOH = 13 mM/min). Between pHi 7.1 and 7.3, the range normally observed during stimulation of PC, rates of anion exchange increased by 75%. This pHi sensitivity cannot explain the 300-500% increase in anion exchanger activity observed during secretagogue stimulation of PC.

scholarly journals Role of WNK4 and kidney-specific WNK1 in mediating the effect of high dietary K+ intake on ROMK channel in the distal convoluted tubule

2018 ◽  
Vol 315 (2) ◽  
pp. F223-F230 ◽  
Author(s):  
Peng Wu ◽  
Zhong-Xiuzi Gao ◽  
Xiao-Tong Su ◽  
David H. Ellison ◽  
Juliette Hadchouel ◽  
...  
Keyword(s):  
Renal Clearance ◽  
Collecting Duct ◽  
Distal Convoluted Tubule ◽  
Cortical Collecting Duct ◽  
Cell Models ◽  
High K ◽  
Cell Recording ◽  
Clearance Study ◽  
Stimulation Of

With-no-lysine kinase 4 (WNK4) and kidney-specific (KS)-WNK1 regulate ROMK (Kir1.1) channels in a variety of cell models. We now explore the role of WNK4 and KS-WNK1 in regulating ROMK in the native distal convoluted tubule (DCT)/connecting tubule (CNT) by measuring tertiapin-Q (TPNQ; ROMK inhibitor)-sensitive K+ currents with whole cell recording. TPNQ-sensitive K+ currents in DCT2/CNT of KS- WNK1−/− and WNK4−/− mice were significantly smaller than that of WT mice. In contrast, the basolateral K+ channels (a Kir4.1/5.1 heterotetramer) in the DCT were not inhibited. Moreover, WNK4−/− mice were hypokalemic, while KS- WNK1−/− mice had normal plasma K+ levels. High K+ (HK) intake significantly increased TPNQ-sensitive K+ currents in DCT2/CNT of WT and WNK4−/− mice but not in KS- WNK1−/− mice. However, TPNQ-sensitive K+ currents in the cortical collecting duct (CCD) were normal not only under control conditions but also significantly increased in response to HK in KS- WNK1−/− mice. This suggests that the deletion of KS-WNK1-induced inhibition of ROMK occurs only in the DCT2/CNT. Renal clearance study further demonstrated that the deletion of KS-WNK1 did not affect the renal ability of K+ excretion under control conditions and during increasing K+ intake. Also, HK intake did not cause hyperkalemia in KS- WNK1−/− mice. We conclude that KS-WNK1 but not WNK4 is required for HK intake-induced stimulation of ROMK activity in DCT2/CNT. However, KS-WNK1 is not essential for HK-induced stimulation of ROMK in the CCD, and the lack of KS-WNK1 does not affect net renal K+ excretion.

Halide transport patterns of apical anion exchange in rabbit cortical collecting duct intercalated cells

1996 ◽  
Vol 271 (4) ◽  
pp. F799-F805 ◽  
Author(s):  
C. Emmons
Keyword(s):  
Anion Exchange ◽  
Intracellular Ph ◽  
Anion Exchanger ◽  
Collecting Duct ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Intracellular Acidification ◽  
Transport Patterns ◽  
Exchange Activity

To investigate halide selectivity patterns of cortical collecting duct (CCD) intercalated cells (ICs), intracellular pH (pHi) was measured in perfused rabbit outer CCD ICs in Na(+)-free, HCO-3-buffered, 115 mM Cl solutions. Apical anion exchange activity was measured as the dpH/dt after lumen Cl- replacement with gluconate. The perfusate was randomly changed to equimolar Br-, F-, or I-. Addition of Br- to the lumen in place of gluconate caused a brisk acidification similar to that with Cl- return. The acidification rate with I- replacement was only approximately 25% of that seen with Cl- readdition, and F- substitution resulted in a small alkalinization. In a separate protocol, each halide was substituted for lumen Cl-. Replacement of lumen Cl- with Br- resulted in intracellular acidification, whereas F- substitution caused an increase in pHi similar to that with gluconate. A slower rate of alkalinization was seen with I-. Separate tubules were perfused and bathed in Cl(-)-free gluconate solutions for 10 min, and then either Cl- or Br- was returned to the lumen. Similar rates of acidification were found with either Cl- or Br- return. Taken together, the results show that, at a halide concentration of 115 mM, the halide selectivity transport pattern of the apical anion exchanger of CCD ICs is Cl- = Br- > I- > F-.

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.

Modulation of aldosterone-induced stimulation of ENaC synthesis by changing the rate of apical Na+ entry

2001 ◽  
Vol 281 (4) ◽  
pp. F687-F692 ◽  
Author(s):  
Lisette Dijkink ◽  
Anita Hartog ◽  
Carel H. Van Os ◽  
René J. M. Bindels
Keyword(s):  
Feedback Inhibition ◽  
Collecting Duct ◽  
Short Circuit ◽  
Primary Cultures ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Cortical Collecting Duct ◽  
Entry Rate ◽  
Protein Levels ◽  
Stimulation Of

Primary cultures of immunodissected rabbit connecting tubule and cortical collecting duct cells were used to investigate the effect of apical Na+ entry rate on aldosterone-induced transepithelial Na+ transport, which was measured as benzamil-sensitive short-circuit current ( I sc). Stimulation of the apical Na+ entry, by long-term short-circuiting of the monolayers, suppressed the aldosterone-stimulated benzamil-sensitive I sc from 320 ± 49 to 117 ± 14%, whereas in the presence of benzamil this inhibitory effect was not observed (335 ± 74%). Immunoprecipitation of [35S]methionine-labeled β-rabbit epithelial Na+ channel (rbENaC) revealed that the effects of modulation of apical Na+ entry on transepithelial Na+ transport are exactly mirrored by β-rbENaC protein levels, because short-circuiting the monolayers decreased aldosterone-induced β-rbENaC protein synthesis from 310 ± 51 to 56 ± 17%. Exposure to benzamil doubled the β-rbENaC protein level to 281 ± 68% in control cells but had no significant effect on aldosterone-stimulated β-rbENaC levels (282 ± 68%). In conclusion, stimulation of apical Na+ entry suppresses the aldosterone-induced increase in transepithelial Na+transport. This negative-feedback inhibition is reflected in a decrease in β-rbENaC synthesis or in an increase in β-rbENaC degradation.

Basolateral Na(+)-independent Cl(-)-HCO3- exchange in primary cultures of rat IMCD cells

1992 ◽  
Vol 263 (3) ◽  
pp. F401-F410 ◽  
Author(s):  
J. A. Kraut ◽  
D. Hart ◽  
E. P. Nord
Keyword(s):  
Steady State ◽  
Cell Surface ◽  
Primary Culture ◽  
Anion Exchange ◽  
Collecting Duct ◽  
Primary Cultures ◽  
Disulfonic Acid ◽  
Absolute Requirement ◽  
Ethanesulfonic Acid ◽  
Base Load

The role of anion exchange in the regulation of intracellular pH (pHi) under base load and steady-state conditions was investigated in confluent monolayers of rat inner medullary collecting duct (IMCD) cells in primary culture using the pH-sensitive fluoroprobe 2,7-bis(carboxyethyl)-5(6')-carboxyfluorescein (BCECF). Recovery of pHi after imposition of a base load induced either by replacement of HCO3-/CO2 by N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) at the same extracellular pH (pHo) or deletion of Cl- from a HCO3-/CO2-buffered solution had an absolute requirement for Cl-, was Na+ independent, and was inhibited approximately 90% by 50 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). When pHo was decreased by lowering HCO3- concentration in the constant presence of 5% CO2, the rate of decrement in pHi was significantly blunted in the absence of Cl-. Imposition of a positive or negative diffusion potential of equal but opposite magnitude did not modify the anion exchange rate, confirming the electroneutrality of the process. Under steady-state conditions, pHi of cells bathed in a HCO3-/CO2-buffered solution was 7.33 +/- 0.06, significantly lower than that of cells bathed in a nominally HCO3-/CO2-free buffer (7.50 +/- 0.04), indicating that under physiological conditions the pathway functions as a base extruder. In studies performed on cells grown on permeable supports, the anion exchange pathway was found to be confined exclusively to the basolateral-equivalent cell surface. In summary, confluent monolayers of rat IMCD cells in primary culture possess a Na(+)-independent, DIDS-inhibitable electroneutral Cl(-)-HCO3- exchange pathway that is confined to the basolateral cell surface. The transporter is an important determinant of steady-state pHi and is the predominant mechanism whereby the cell recovers from imposed elevations in pHi.

scholarly journals Mechanoregulation of BK channel activity in the mammalian cortical collecting duct: role of protein kinases A and C

2009 ◽  
Vol 297 (4) ◽  
pp. F904-F915 ◽  
Author(s):  
Wen Liu ◽  
Yuan Wei ◽  
Peng Sun ◽  
Wen-Hui Wang ◽  
Thomas R. Kleyman ◽  
...  
Keyword(s):  
Flow Rate ◽  
Collecting Duct ◽  
Bk Channel ◽  
Slow Flow ◽  
Cortical Collecting Duct ◽  
Flow Rates ◽  
Calphostin C ◽  
Flow Stimulation ◽  
Slow Flow Rate ◽  
Stimulation Of

Flow-stimulated net K secretion ( JK) in the cortical collecting duct (CCD) is mediated by an iberiotoxin (IBX)-sensitive BK channel, and requires an increase in intracellular Ca2+ concentration ([Ca2+]i). The α-subunit of the reconstituted BK channel is phosphorylated by PKA and PKC. To test whether the BK channel in the native CCD is regulated by these kinases, JK and net Na absorption ( JNa) were measured at slow (∼1) and fast (∼5 nl·min−1·mm−1) flow rates in rabbit CCDs microperfused in the presence of mPKI, an inhibitor of PKA; calphostin C, which inhibits diacylglycerol binding proteins, including PKC; or bisindolylmaleimide (BIM) and Gö6976, inhibitors of classic and novel PKC isoforms, added to luminal (L) and/or basolateral (B) solutions. L but not B mPKI increased JK in CCDs perfused at a slow flow rate; a subsequent increase in flow rate augmented JK modestly. B mPKI alone or with L inhibitor abolished flow stimulation of JK. Similarly, L calphostin C increased JK in CCDs perfused at slow flow rates, as did calphostin C in both L and B solutions. The observation that IBX inhibited the L mPKI- and calphostin C-mediated increases in JK at slow flow rates implicated the BK channel in this K flux, a notion suggested by patch-clamp analysis of principal cells. The kinase inhibited by calphostin C was not PKC as L and/or B BIM and Gö6976 failed to enhance JK at the slow flow rate. However, addition of these PKC inhibitors to the B solution alone or with L inhibitor blocked flow stimulation of JK. Interpretation of these results in light of the effects of these inhibitors on the flow-induced elevation of [Ca2+]i suggests that the principal cell apical BK channel is tonically inhibited by PKA and that flow stimulation of JK in the CCD is PKA and PKC dependent. The specific targets of the kinases remain to be identified.

Regulation of maturation and processing of ENaC subunits in the rat kidney

2006 ◽  
Vol 291 (3) ◽  
pp. F683-F693 ◽  
Author(s):  
Zuhal Ergonul ◽  
Gustavo Frindt ◽  
Lawrence G. Palmer
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Na Channel ◽  
Cortical Collecting Duct ◽  
Α Subunit ◽  
Salt Restriction ◽  
High K ◽  
Electrophysiological Measurements ◽  
Immature Form ◽  
Epithelial Na Channel

Antibodies directed against subunits of the epithelial Na channel (ENaC) were used together with electrophysiological measurements in the cortical collecting duct to investigate the processing of the proteins in rat kidney with changes in Na or K intake. When animals were maintained on a low-Na diet for 7–9 days, the abundance of two forms of the α-subunit, with apparent masses of 85 and 30 kDa, increased. Salt restriction also increased the abundance of the β-subunit and produced an endoglycosidase H (Endo H)-resistant pool of this subunit. The abundance of the 90-kDa form of the γ-subunit decreased, whereas that of a 70-kDa form increased and this peptide also exhibited Endo H-resistant glycosylation. These changes in α- and γ-subunits were correlated with increases in Na conductance elicited by a 4-h infusion with aldosterone. Changes in all three subunits were correlated with decreases in Na conductance when Na-deprived animals drank saline for 5 h. We conclude that ENaC subunits are mainly in an immature form in salt-replete rats. With Na depletion, the subunits mature in a process that involves proteolytic cleavage and further glycosylation. Similar changes occurred in α- and γ- but not β-subunits when animals were treated with exogenous aldosterone, and in β- and γ- but not α-subunits when animals were fed a high-K diet. Changes in the processing and maturation of the channels occur rapidly enough to be involved in the daily regulation of ENaC activity and Na reabsorption by the kidney.

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