Inhibition of H⁺ efflux and K⁺ uptake, and induction of K⁺ efflux in yeast by heavy metals

Energy and cell membrane ATPase‐dependent H⁺ efflux from yeast cells was inhibited by heavy metals, which also inhibited energy‐dependent K⁺ uptake by the cells. Heavy metals also induced K⁺ efflux from metabolizing cells in two phases: reversibly at low concentrations and irreversibly at high concentrations. The concentration dependence of all of these effects varied considerably between metals. The effect of in vivo inhibition of H⁺ transporting ATPases on cell membrane polarization and thus on cellular transport processes, including heavy metal uptake, are discussed. It is proposed that the inhibition of H⁺ efflux and the appearance of irreversible K⁺ efflux in yeast are potentially useful indicators of heavy metal toxicity toward yeast and possibly other fungi.