Membrane damage by lipid peroxidation retains the cadmium constraint and is not the primary cause of K+ extrusion in yeast

Abstract

Yeast cells exposed to cadmium (Cd) generate free radicals that cause disruption of membranes, possibly induced by elevated levels of lipid peroxidation with associated K+ efflux. The influence of lipid peroxidation on cadmium incorporation and the relationship of lipid oxidation with sodium/potassium movement was investigated. Mutant ahp1∆ [alkyl hydroperoxidase reductase (AHP1) gene deletion] was used. ahp1∆ mutant showed a lipid peroxidation index higher than wild type (WT) independently of the presence of cadmium. Despite lipid peroxidation being generally correlated to membrane permeabilization, cadmium incorporation was similar in both strains. The Na+ level was higher in ahp1∆ mutant compared to WT cells. Cd treatment tended to restore the Na+ level in mutant cells to similar levels determined in WT cells. Cd induced a lower K+ efflux than that for sodium exit. We point out the possible influence of glutathione on potassium efflux as the first cause of ionic movement and the influence of the AHP1 gene on ionic movement.