We examined pHi and its regulation in isolated nonperfused proximal tubules of chicken loopless nephrons (70-90% of nephrons in kidney) using pH-sensitive fluorescent dye BCECF. Under control conditions (HEPES buffer, pH 7.4; 37°C) resting pH was 7.18 ± 0.02 (mean ± SE). Addition of 20 mM NH4Cl to bath increased pH to 7.68 ± 0.03. Removal of NH4Cl from bath reduced pH to 6.95 ± 0.03. Rate of pHi change (dpHi/dt, pH U/s), intrinsic buffering capacity (βi, mM H+/pH U), basolateral NH3 flux (JNH3, nmol/cm2/s), and basolateral NH3 permeability (PNH3, cm/s × 10-3) were, respectively: 0.13 ± 0.01, 27.55 ± 3.42, 1.86 ± 0.16, and 3.80 ± 0.32. Control recovery rate (dpHi/dt) from acid pHi after NH4Cl removal was 4.98 ± 0.38 × 10-3 pH U/s. This dpHi/df was significantly (P < 0.05; paired studies) decreased by removal of Na+ (replacement with N-methyl-D-glucamine Cl-), simultaneous removal of Na+ and Cl- (replacement with N-methyl-D-glucamine-gluconate), or addition of DIDS, significantly increased by high K+ (75 mM) (depolarization of basolateral membrane); and unchanged by removal of Cl- (replacement with Na+-gjuconate) or addition of EIPA (1 mM) or Ba2+ (basolateral depolarization; blockage of K+ channels) Resting pH was significantly (P < 0.05; paired studies) decreased by Na+ removal or simultaneous Na+ and Cl- removal; significantly increased by high K+; and unchanged by Cl- removal alone or addition of Ba2+. Data do not fit concept of pHi regulation by usual basolateral transporters (Na+/H+ exchange; Na+-dependent and Na+-independent Cl- /HCO3- exchange; or Na+-HCO3--CO32- cotransporter). There may be Na--HCO3 cotransporter for basolateral HCO3- entry.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology