Effect of various detergents on kinetic characteristics of lipid peroxidation systems in rat liver microsomes

Abstract

The vari-directional and biphasic actions of detergents on the lipid peroxidation (LP) in microsome systems have been demonstrated in our experiments. Anionic detergents deoxycholate (DOC) and sodium dodecyl sulfate (SDS), when applied in relatively small concentrations, activate the ascorbate-dependent LP and lower the K m for iron ions in ascorbate-dependent and in NADPH-dependent LP. Besides, DOC weakens the inhibiting influence of promethazine and EDTA on both LP systems. The nonionic detergent Triton X-100 does not affect the investigated characteristics of peroxidation in microsomal lipids. The cationic detergent cetyltrimethylammonium bromide inhibits both LP microsome systems and raises the K m for iron ions in these reactions. Comparatively high concentrations of DOC, SDS, and Triton X-100 suppress both the NADPH- and ascorbate-dependent LP reactions in the microsomes. A reasonable hypothesis is that involvement of anionic detergents in the microsome membrane is attended by an increase in iron ion binding, whereas inclusion of cationic detergents results in a reverse effect. Under discussion is the interconnection between the amount of radical-forming centers, essential components of which are iron ions, and LP activity in the microsomes.