Intracellular pH (pH(i)) and its basolateral regulation were studied in isolated proximal-proximal and distal-proximal segments of garter snake (Thamnophis spp.) renal tubules with oil-filled lumens in HEPES-buffered and in HEPES-HCO3/--buffered media (pH 7.4 at 25°C). pH(i) was measured with the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5,6- carboxyfluorescein (BCECF) under resting conditions and in response to NH4Cl pulse. Resting pH(i) (~7.1-7.2) and its response to and rate of recovery (dpH(i)/dt) from an NH4Cl pulse were not affected by the presence or absence of HCO3/- in either segment. Rate of recovery was depressed by Na+ removal in distal-proximal segments only and only in HEPES buffer. It was not affected by removal of Cl- or of both Na+ and Cl- or by reduction in membrane potential through addition of Ba2+ (5 mM) or high K+ (75 mM) in either segment in either HEPES or HEPES-HCO3/- buffer. The Na+/H+ exchange inhibitor ethylisopropylamiloride (EIPA) (100 μM) and the anion exchange inhibitor DIDS (100 μM) reduced dpH(i)/dt in the distal-proximal segments only and only in HEPES-HCO3 buffer. The H+-ATPase inhibitor bafilomycin (1 μM), H+-K+-ATPase and K+/NH4/+ exchange inhibitor Schering 28080 (10-100 μM), organic cation efflux inhibitor tetrapentylammonium (25 μM-20 mM), and K+ channel blocker tetraethylammonium (20 mM) had no effect on dpH(i)/dt in either segment. These data do not clearly support basolateral regulation of pH(i) in snake proximal renal tubules by commonly recognized Na+-dependent or Na+- independent acid or base transporters.
|Original language||English (US)|
|Journal||American Journal of Physiology - Regulatory Integrative and Comparative Physiology|
|Issue number||6 45-6|
|State||Published - Jun 1999|
- Ammonium chloride pulse
- Garter snakes
- Schering 28080
- Thamnophis spp.