Am. J. Respir. Crit. Care Med., Vol 155, No. 2, Feb 1997, 597-602.
Intracellular pH regulation in cultured human pleural mesothelial cells
YS Liaw, PC Yang, CJ Yu, SH Kuo, KT Luh, YJ Lin and ML Wu
Department of Internal Medicine, College of Medicine, National Taiwan University, Taipei, R.O.C.
The human pleural space is lined by a single layer of mesothelial cells,
the intracellular pH (pH(i)) of which has never been investigated. In the
present study, the intrinsic buffering power of H+ ions (beta(i)) and the
pH(i) regulatory systems were investigated in primary cultures of human
pleural mesothelial cells (PMCs) with microspectrofluorimetry. We found:
(1) that at the resting pH(i), the beta(i) was low and increased as the
pH(i) decreased; (2) that the pH(i) recovery was largely inhibited either
with Na+-free medium or nominally HCO3 free medium containing
ethyl-isopropyl amiloride (EIPA); (3) a
4-4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)- sensitive,
Na+/HCO3-dependent, but Cl(-)-independent acid extrusion mechanism in
CO2/HCO3 buffer; and (4) that in the same buffer, a DIDS- sensitive but
Na+-independent alkalosis was induced by intracellular Cl- depletion. We
therefore conclude that at least three membrane pH(i) regulators are
involved in regulating the pH(i) in PMCs, these being the EIPA-sensitive
Na+-H+ exchanger; a novel electroneutral, DIDS- sensitive Na+-HCO3
cotransporter; and the DIDS-sensitive Cl(-)-HCO3 exchanger. Furthermore,
under physiologic conditions, the Na+-HCO3 cotransporter plays a more
important role in extrusion of excess intracellular H+ ions than does the
Na+-H+ exchanger.
