Effect of changes in extracellular potassium on intracellular pH in principal cells of frog skin.

Intracellular pH (pHi), apical membrane potential (Va), and fractional apical membrane resistance (FRa) 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 FRa and pHi. 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 HCO3- and in presence of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Under all these conditions pHi moved toward electrochemical equilibrium. Reduced basolateral K+ hyperpolarized V(a) and decreased pHi. The data suggest that depolarization and hyperpolarization of the apical and/or basolateral membrane are associated with an increase and decrease, respectively, in pHi without involvement of Na(+)-H+, Cl(-)-HCO3-, 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 pHi regulation and signal transduction.