Viability and formation of conjugated dienes in plasma membrane lipids of Saccharomyces cerevisiae, Schizosaccharomyces pombe, Rhodotorula glutinis and Candida albicans exposed to hydrophilic, amphiphilic and hydrophobic pro-oxidants.

Effects of four lipid peroxidation-inducing pro-oxidants--amphiphilic tert-butyl hydroperoxide (TBHP), hydrophobic 1,1'-azobis(4-cyclohexanecarbonitrile) (ACHN), hydrophilic FeII and 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH)--on cell growth and on generation of peroxidation products in isolated plasma membrane lipids were determined in four yeast species (S. cerevisiae, S. pombe, R. glutinis and C. albicans) differing in their plasma membrane lipid composition. TBHP and ACHN inhibited cell growth most strongly, FeII and AAPH exerted inhibitory action for about 2 h, with subsequent cell growth resumption. S. cerevisiae strain SP4 was doped during growth with unsaturated linoleic (18:2) and linolenic (18:3) acids to change its resistance to lipid peroxidation. Its plasma membranes then contained some 30% of these acids as compared with some 1.3% of 18:2 acid found in undoped S. cerevisiae, while the content of (16:1) and (18:1) acids was lower than in undoped S. cerevisiae. The presence of linoleic and linolenic acids in S. cerevisiae cells lowered cell survival and increased the sensitivity to pro-oxidants. Peroxidation-generated conjugated dienes (CD) were measured in pure TBHP- and ACHN-exposed fatty acids used as standards. The CD level depended on the extent of unsaturation and the pro-oxidant used. The TBHP-induced CD production in a mixture of oleic acid and its ester was somewhat lower than in free acid and ester alone. In lipids isolated from the yeast plasma membranes, the CD production was time-dependent and decreased after a 5-15-min pro-oxidant exposure. ACHN was less active than TBHP. The most oxidizable were lipids from S. cerevisiae plasma membranes doped with linoleic and linolenic acids and from C. albicans with indigenous linolenic acid.