Effects of inhibitors of plasma-membrane ATPase on potassium and calcium fluxes, membrane potential and proton motive force in the yeast Saccharomyces cerevisiae.

The plasma membrane ATPase inhibitors N,N-dicyclohexylcarbodiimide (DCCD), diethylstilboestrol and sodium orthovanadate caused inhibition of proton ejection in Saccharomyces cerevisiae at a concentration range of 0.1-0.4 mM. At this concentration K+ efflux was not observed; DCCD caused K+ efflux only at a much higher concentration (2mM). It was shown that induction of K+ efflux by DCCD was not mediated via inhibition of ATPase and that it may be the result of a direct effect of the drug on the cell membrane or on the K+ carrier. All three inhibitors also caused mild hyperpolarization of the membrane and an increase in the carrier mediated Ca2+ uptake into the cells. The increase in delta psi balanced the decrease in delta pH so that the value of delta mu H+ changed very little following incubation of the cells with the inhibitors. The respiratory deficient mutant ('petite') displayed similar phenomena to the wild type, but membrane potential values were lower than in the wild type.