Na+-H+ exchange activity in rat hepatocytes: role in regulation of intracellular pH

摘要: Amiloride-sensitive Na+-H+ exchange has been identified in basolateral membrane vesicles from rat liver, but little is currently known about its regulation or role maintenance of resting intracellular pH (pHi) intact hepatocytes. We have assessed activity isolated cultured hepatocytes nominally HCO3- free solution under basal conditions and after acidification by an NH4Cl pulse measuring 1) pHi, using the pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxy fluorescein, 2) net H+ efflux pH-stat titration, 3) amiloride-inhibitable 22Na uptake. Under conditions, did not contribute measurably to Na+ uptake accounted for less than 20% efflux. Hepatocyte pHi averaged 7.07 +/- 0.03, significantly above electrochemical equilibrium (6.92 0.08) determined electrogenic proton ionophore. Transient removal extracellular exposure amiloride reversibly lowered 0.09 0.01 0.12 0.03 units, respectively, within 5-10 min. After pulse, rate increased twofold, increase being entirely inhibitable. Net threefold, 70% was Recovery blocked Na+. (calculated change buffering capacity) inversely related estimated approach zero at 7.25-7.50.(ABSTRACT TRUNCATED AT 250 WORDS)