Effects of bafilomycin A1 on cytosolic pH of sheep alveolar and peritoneal macrophages: evaluation of the pH-regulatory role of plasma membrane V-ATPases.
The role of plasma membrane V-ATPase activity in the regulation of cytosolic pH (pHi) was determined for resident alveolar and peritoneal macrophages (m theta) from sheep. Cytosolic pH was measured using 2',7'-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). The baseline pHi of both cell types was sensitive to the specific V-ATPase inhibitor bafilomycin A1. Bafilomycin A1 caused a significant (approximately 0.2 pH units) and rapid (within seconds) decline in baseline pHi. Further, bafilomycin A1 slowed the initial rate of pHi recovery (dpHi/dt) from intracellular acid loads. Amiloride had no effects on baseline pHi, but reduced dpHi/dt (acid-loaded pHi nadir < 6.8) by approximately 35%. Recovery of pHi was abolished by co-treatment of m theta with bafilomycin A1 and amiloride. These data indicate that plasma membrane V-ATPase activity is a major determinant of pHi regulation in resident alveolar and peritoneal m theta from sheep. Sheep m theta also appear to possess a Na+/H+ exchanger. However, Na+/H+ exchange either is inactive or can be effectively masked by V-ATPase-mediated H+ extrusion at physiological pHi values.
Heming
T A
TA
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555-0876, USA.
Traber
D L
DL
Hinder
F
F
Bidani
A
A
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology*; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D018942:Macrolides; D017737:Macrophages, Peritoneal / Q000187:drug effects*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000187:drug effects*; D012756:Sheep; D014617:Vacuoles / Q000201:enzymology
D000900:Anti-Bacterial Agents; D005452:Fluoresceins; D018942:Macrolides; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; C040929:bafilomycin A1; D006180:Proton-Translocating ATPases