scholarly journals Intracellular pH regulation in freshly isolated suspensions of rabbit inner medullary collecting duct cells: role of Na+:H+ antiporter and H(+)-ATPase.

1990 ◽  
Vol 1 (6) ◽  
pp. 890-901
Author(s):  
D Kikeri ◽  
M L Zeidel
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Intracellular Ph ◽  
Recovery Rate ◽  
Collecting Duct ◽  
Atp Depletion ◽  
Cell Membrane Potential ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct ◽  
In Cells

To define proton transport mechanisms involved in the regulation of intracellular pH (pHi) in cells of the inner medullary collecting duct (IMCD), pHi and cell membrane potential were estimated by using the fluorescent dyes 2,7-biscarboxyethyl-5(6)-carboxyfluorescein and 3,3'-dipropylthiadicarbocyanine iodide, respectively, in suspensions of freshly isolated rabbit IMCD cells. The resting pHi of IMCD cells in nonbicarbonate Ringer's solution (pH 7.4) was 7.21 +/- 0.03 (mean +/- SE). When cells were acidified by ammonium withdrawal, the initial pHi recovery rate was 0.33 +/- 0.02 pH unit/min; replacement of extracellular Na+ (130 mM) with N-methyl-D-glucamine+ reduced the pHi recovery rate to 0.08 +/- 0.02 pH unit/min, while addition of 0.1 mM amiloride in the presence of extracellular Na+ reduced the rate of pHi recovery to 0.02 +/- 0.02 pH unit/min. Similar results were obtained in cells acid loaded with HCl. Cells recovering from acidification exhibited 22Na+ uptake rates threefold higher than did nonacidified cells. The rate of Na(+)-dependent pHi recovery was independent of the cell membrane potential. In the absence of extracellular Na+, depolarizing cell membrane potential in a stepwise manner by increasing extracellular K+ concentrations from 1 to 130 mM resulted in graded increments in the rate of pHi recovery. In the presence of 130 mM K+, the pHi recovery rate in acidified cells was dependent on cellular ATP levels, sensitive to 1 mM N-ethylmaleimide, and insensitive to 0.01 mM oligomycin in the presence of glucose (control, 0.24 +/- 0.01; ATP-depleted, 0.13 +/- 0.02; addition of N-ethylmaleimide, 0.16 +/- 0.01; addition of oligomycin, 0.27 +/- 0.02 pH unit/min). ATP depletion markedly inhibited H+ extrusion from IMCD cells measured by using a pH stat. These results provide direct evidence in freshly isolated IMCD cells that both a Na+:H+ antiporter and a rheogenic H(+)-ATPase participate in pHi regulation.

Cellular pathways of potassium transport in renal inner medullary collecting duct

1989 ◽  
Vol 256 (4) ◽  
pp. C823-C830 ◽  
Author(s):  
B. C. Kone ◽  
D. Kikeri ◽  
M. L. Zeidel ◽  
S. R. Gullans
Keyword(s):  
Membrane Potential ◽  
Oxidative Phosphorylation ◽  
Collecting Duct ◽  
Iodoacetic Acid ◽  
Mitochondrial Oxidative Phosphorylation ◽  
Transport Pathways ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct ◽  
Cellular Pathways ◽  
K Transport

The dominant K+ transport pathways in rabbit inner medullary collecting duct (IMCD) cells were identified using an extracellular K+ electrode and fluorometric estimates of membrane potential. Ba2+ (5 mM) caused an initial rate of net K+ influx (61 +/- 6 nmol K+.min-1. mg protein-1) equivalent to the net K+ efflux (59 +/- 5 nmol K+. min-1.mg protein-1) induced by ouabain (0.1 mM). Addition of ouabain to Ba2+ -treated cells caused no net K+ flux. Membrane potential experiments demonstrated a K+ conductance that was inhibited by Ba2+. Thus K+ transport in the IMCD occurs principally via Ba2+ -sensitive K+ conductive pathway(s) and Na+-K+-ATPase. In studies that examine the metabolic determinants of K+ transport in the IMCD, glucose (but not 3-O-methylglucose) augmented oxygen consumption (QO2; + 12%) and cell K+ content (+12%), whereas iodoacetic acid, an inhibitor of glycolysis, promoted a release of cell K+. However, inhibition of mitochondrial oxidative phosphorylation with rotenone demonstrated that glycolysis alone could not maintain cell K+ content. Thus glucose metabolism plays an important role in K+ transport in the IMCD, but both glycolysis and oxidative phosphorylation are required to maintain optimal cellular K+ gradients.

scholarly journals Intracellular pH regulation in the inner medullary collecting duct of the hamster kidney.

1989 ◽  
Vol 49 ◽  
pp. 56
Author(s):  
Yohkazu Matsushima ◽  
Koji Yoshitomi ◽  
Chizuko Koseki ◽  
Masashi Imai ◽  
Satoshi Akahane ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Ph Regulation ◽  
Collecting Duct ◽  
Intracellular Ph Regulation ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct

scholarly journals Bradykinin-induced oscillations of cell membrane potential in cells expressing the Ha-ras oncogene.

1991 ◽  
Vol 266 (8) ◽  
pp. 4938-4942
Author(s):  
F Lang ◽  
F Friedrich ◽  
E Kahn ◽  
E Wöll ◽  
M Hammerer ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Cell Membrane Potential ◽  
Ras Oncogene ◽  
In Cells

scholarly journals Disruption of KCNJ10 (Kir4.1) stimulates the expression of ENaC in the collecting duct

2016 ◽  
Vol 310 (10) ◽  
pp. F985-F993 ◽  
Author(s):  
Xiao-Tong Su ◽  
Chengbiao Zhang ◽  
Lijun Wang ◽  
Ruimin Gu ◽  
Dao-Hong Lin ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Reversal Potential ◽  
Renal Medulla ◽  
Cell Membrane Potential ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Wild Type

Kcnj10 encodes the inwardly rectifying K+ channel 4.1 (Kir4.1) and is expressed in the basolateral membrane of late thick ascending limb, distal convoluted tubule (DCT), connecting tubule (CNT), and cortical collecting duct (CCD). In the present study, we perform experiments in postneonatal day 9 Kcnj10−/− or wild-type mice to examine the role of Kir.4.1 in contributing to the basolateral K+ conductance in the CNT and CCD, and to investigate whether the disruption of Kir4.1 upregulates the expression of the epithelial Na+ channel (ENaC). Immunostaining shows that Kir4.1 is expressed in the basolateral membrane of CNT and CCD. Patch-clamp studies detect three types of K+ channels (23, 40, and 60 pS) in the basolateral membrane of late CNT and initial CCD in wild-type (WT) mice. However, only 23- and 60-pS K+ channels but not the 40-pS K+ channel were detected in Kcnj10−/− mice, suggesting that Kir.4.1 is a key component of the 40-pS K+ channel in the CNT/CCD. Moreover, the depletion of Kir.4.1 did not increase the probability of finding the 23- and 60-pS K+ channel in the CNT/CCD. We next used the perforated whole cell recording to measure the K+ reversal voltage in the CNT/CCD as an index of cell membrane potential. Under control conditions, the K+ reversal potential was −69 mV in WT mice and −61 mV in Kcnj10−/− mice, suggesting that Kir4.1 partially participates in generating membrane potential in the CNT/CCD. Western blotting and immunostaining showed that the expression of ENaCβ and ENaCγ subunits from a renal medulla section of Kcnj10−/− mice was significantly increased compared with that of WT mice. Also, the disruption of Kir4.1 increased aquaporin 2 expression. We conclude that Kir4.1 is expressed in the CNT and CCD and partially participates in generating the cell membrane potential. Also, increased ENaC expression in medullary CD of Kcnj10−/− mice is a compensatory action in response to the impaired Na+ transport in the DCT.

Mechanisms of intracellular pH regulation in the hamster inner medullary collecting duct perfused in vitro

1990 ◽  
Vol 416 (6) ◽  
pp. 715-721 ◽  
Author(s):  
Yohkazu Matsushima ◽  
Koji Yoshitomi ◽  
Chizuko Koseki ◽  
Minoru Kawamura ◽  
Satoshi Akabane ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Ph Regulation ◽  
Collecting Duct ◽  
Intracellular Ph Regulation ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct

H(+)-K(+)-ATPase of rat inner medullary collecting duct in primary culture

1993 ◽  
Vol 265 (5) ◽  
pp. F698-F704
Author(s):  
J. G. Kleinman ◽  
P. Tipnis ◽  
R. Pscheidt
Keyword(s):  
Atpase Activity ◽  
Recovery Rate ◽  
Ph Regulation ◽  
Collecting Duct ◽  
Primary Cultures ◽  
Significant Inhibition ◽  
Atpase Inhibitor ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct ◽  
P Type

pH recovery in response to addition of and removal from NH4Cl was examined using 2',7'-bis(2-carboxy-ethyl)-5(6)-carboxyfluorescein fluorescence in primary cultures of inner medullary collecting duct (IMCD) cells from rat kidneys. In 0 K+, pH recovery rate was 0.012 +/- 0.010 U/min; in 5 mM K+, the recovery rate was greater at 0.065 +/- 0.013 U/min (P = 0.026). The H(+)-K(+)-adenosinetriphosphatase (H(+)-K(+)-ATPase) inhibitors omeprazole and Sch-28080 and the P-type ATPase inhibitor vanadate significantly inhibited pH recovery at 100, 10, and 5 microM, respectively. The vacuolar H(+)-ATPase inhibitor bafilomycin failed to inhibit pH recovery, but N-ethylmaleimide (NEM) did. A range of Sch-28080 concentrations inhibited ouabain-resistant ATPase activity of microsomes from these cells in a reverse sigmoidal manner, with little inhibition < 1 microM, virtually 100% inhibition > 100 microM, and a 50% inhibitory concentration of approximately 20 microM. Bafilomycin only produced significant inhibition of activity at concentrations well in excess of those that are effective against the vacuolar H(+)-ATPase. The ouabain-resistant ATPase activity in cultured IMCD was also sensitive to vanadate (90% inhibition with 5 microM) but relatively resistant to N,N'-dicyclohexylcarbodiimide and NEM. These results indicate that pH regulation in primary cultures of IMCD cells, presumably reflecting H+ transport, is predominantly due to an H(+)-K(+)-ATPase.

scholarly journals A mathematical model of the inner medullary collecting duct of the rat: pathways for Na and K transport

1998 ◽  
Vol 274 (5) ◽  
pp. F841-F855 ◽  
Author(s):  
Alan M. Weinstein
Keyword(s):  
Mathematical Model ◽  
Cell Membrane ◽  
Collecting Duct ◽  
High Rate ◽  
Inner Medullary Collecting Duct ◽  
Luminal Membrane ◽  
Medullary Collecting Duct ◽  
Model Features ◽  
Novel Model ◽  
Nacl Cotransport

A mathematical model of the inner medullary collecting duct (IMCD) of the rat has been developed representing Na+, K+, Cl−,[Formula: see text] CO2, H2CO3, phosphate, ammonia, and urea. Novel model features include: finite rates of hydration of CO2, a kinetic representation of the H-K-ATPase within the luminal cell membrane, cellular osmolytes that are regulated in defense of cell volume, and the repeated coalescing of IMCD tubule segments to yield the ducts of Bellini. Model transport is such that when entering Na+ is 4% of filtered Na+, approximately 75% of this load is reabsorbed. This requirement renders the area-specific transport rate for Na+ comparable to that for proximal tubule. With respect to the luminal membrane, there is experimental evidence for both NaCl cotransport and an Na+ channel in parallel. The experimental constraints that transepithelial potential difference is small and that the fractional apical resistance is greater than 85% mandate that more than 75% of luminal Na+ entry be electrically silent. When Na+delivery is limited, an NaCl cotransporter can be effective at reducing luminal Na+ concentration to the observed low urinary values. Given the rate of transcellular Na+ reabsorption, there is necessarily a high rate of peritubular K+recycling; also, given the lower bound on luminal membrane Cl− reabsorption, substantial peritubular Cl− flux must be present. Thus, if realistic limits on cell membrane electrical resistance are observed, then this model predicts a requirement for peritubular electroneutral KCl exit.

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