Basolateral regulation of pHi in isolated snake renal proximal tubules in presence and absence of bicarbonate.
Intracellular pH (pHi) 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-HCO-3-buffered media (pH 7.4 at 25 degrees C). pHi 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 pHi (approximately 7.1-7.2) and its response to and rate of recovery (dpHi/dt) from an NH4Cl pulse were not affected by the presence or absence of HCO-3 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-HCO-3 buffer. The Na+/H+ exchange inhibitor ethylisopropylamiloride (EIPA) (100 microM) and the anion exchange inhibitor DIDS (100 microM) reduced dpHi/dt in the distal-proximal segments only and only in HEPES-HCO-3 buffer. The H+-ATPase inhibitor bafilomycin (1 microM), H+-K+-ATPase and K+/NH+4 exchange inhibitor Schering 28080 (10-100 microM), organic cation efflux inhibitor tetrapentylammonium (25 microM-20 mM), and K+ channel blocker tetraethylammonium (20 mM) had no effect on dpHi/dt in either segment. These data do not clearly support basolateral regulation of pHi in snake proximal renal tubules by commonly recognized Na+-dependent or Na+-independent acid or base transporters.
Dantzler
W H
WH
Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona 85724-5051, USA. dantzler@u.arizona.edu
Serrano
O K
OK
Abbott
D E
DE
Kim
Y K
YK
Brokl
O H
OH
D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002021:Buffers; D017812:Colubridae / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D010539:Permeability; D013268:Stimulation, Chemical
D001639:Bicarbonates; D002021:Buffers; D000643:Ammonium Chloride; D006859:Hydrogen