AJP - Cell Physiology, Vol 260, Issue 1 C159-C166, Copyright © 1991 by American Physiological Society
Regulation of cytosolic pH of cultured mesangial cells by prostaglandin F2 alpha and thromboxane A2
P. Mene, G. R. Dubyak, A. Scarpa and M. J. Dunn
Department of Medicine, Case Western Reserve University School of Medicine, University Hospitals of Cleveland, Ohio 44106.
Prostaglandins (PG) and thromboxane A2 (TxA2) have marked vasoactive
effects on the renal glomerular microcirculation. Exposure of cultured
mesangial cells to PGF2 alpha and TxA2 mimetics results in a rapid
elevation of free cytosolic Ca2+ ([Ca2+]i) followed by contraction and cell
proliferation. We studied whether other ionic changes mediate these effects
of eicosanoids on cells of rat and human origin. Cytoplasmic pH (pHi) was
monitored in cells loaded with the fluorescent, intracellularly trapped
pH-sensitive probe 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein. PGF2
alpha in rat cells and the TxA2 mimetic U-46619 in human cells induced
rapid, dose-dependent cytosolic acidification followed by recovery and net
alkalinization mediated by enhanced Na(+)-H+ exchange. The early
acidification was also stimulated by ionomycin and Ca2(+)-mobilizing
peptides, implicating a Ca2(+)-dependent mechanism. Alkalinization was
abolished by removal of extracellular Na+ and by amiloride. Both components
of the responses were inhibited by phorbol myristate acetate, which could
mimic alkalinization, suggesting a regulatory role of protein kinase C in
activation of the Na(+)-H+ exchanger by eicosanoids. Vasoconstrictor
arachidonate metabolites may control glomerular cell function by a
signaling mechanism centered on concurrent changes of pHi and [Ca2+]i.
