EFFECT OF CHANGES IN EXTRACELLULAR POTASSIUM ON INTRACELLULAR PH IN PRINCIPAL CELLS OF FROG-SKIN

Intracellular pH (pH(i)), apical membrane potential (V(a)), and fractional apical membrane resistance (FR(a)) were measured in principal cells of isolated frog skin (Rana pipiens) with double-barreled microelectrodes under short-circuit and open-circuit conditions. Basolateral exposure to high K+ concentration or Ba2+ depolarized V(a), decreased short-circuit current, and increased FR(a) and pH(i). However, an increase in K+ subsequent to Ba2+ application did not induce additional changes in these parameters. High basolateral K+, previously shown to increase apical K+ secretion (N. S. Bricker, T. Biber, and H. H. Ussing. J. Clin. Invest. 41: 88-99, 1963), also increased apical Na+ conductance. The depolarization and intracellular alkalinization induced by high K+ were also observed in absence of Na+, Cl-, and HCO- and in presence of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Under all these conditions pH(i) moved toward electrochemical equilibrium. Reduced basolateral K+ hyperpolarized V(a) and decreased pH(i). The data suggest that depolarization and hyperpolarization of the apical and/or basolateral membrane are associated with an increase and decrease, respectively, in pH(i) without involvement of Na+-H+, Cl--HCO-, or K+-H+ exchange and are apparently also independent of an active H+ secretion pathway. This indicates the presence of a potential-dependent H+ and/or OH- conductance in the apical and/or basolateral cell membrane that may play an important role in pH(i) regulation and signal transduction.