Effect of sulfhydryl reagents on peroxidation in microsomes

Abstract

Incubation of mouse liver microsomes with HgCl 2, NEM, or PCMB results in the formation of lipid peroxides as measured by the thiobarbituric acid reaction. Carbon monoxide inhibits peroxidation induced by NEM and the inhibition is reversed by light. Peroxidation induced by HgCl 2 is not greatly affected by EDTA but is increased by ascorbic acid. Microsomes isolated from mice pretreated by intraperitoneal injection of HgCl 2 peroxidized endogenous unsaturated lipid on incubation, and addition of HgCl 2 in vitro further increases the peroxidation. The in vitro stimulation of peroxidation by these SH reagents in liver microsomes increases with age in the rat, and microsomes from male rats are more active than those from female. Pretreatment of mice with phenobarbital for 3 days increases the in vitro effect of HgCl 2 on peroxidation. This stimulation occurs in the smooth-surfaced microsomes. Actinomycin partially inhibits the effect of phenobarbital. Mercuric chloride causes no peroxidation on incubation with shark liver microsomes. Urea causes no peroxidation on incubation with mouse liver microsomes. These results are consistent with the possibility that sulfhydryl-reacting agents produce a change in tertiary structure of microsomal Fe x, thereby rendering the protein-bound iron available for catalysis of peroxidation of endogenous lipid.