Lipid peroxidation in purified plasma membrane fractions of rat liver in relation to the hepatoxicity of carbon tetrachloride

Abstract

Preparations of rat liver sinusoidal plasma membrane have been tested for their ability to metabolize the hepatotoxin carbon tetrachloride (CCl₄) to reactive free radicals in vitro and compared in this respect with standard preparations of rat liver microsomes. The sinusoidal plasma membranes were relatively free of endoplasmic reticulum-associated activities such as the enzymes of the cytochrome P₄₅₀ system and glucose-6-phosphatase. CCl₄ metabolism was measured as (i) covalent binding of [¹⁴C]-CCl₄ to membrane protein, (ii) electron spin resonance spin-trapping of CCl₃· radicals and (iii) CCl₄-induced lipid peroxidation. By all of these tests, purified sinusoidal plasma membranes were found unable to metabolize CCl₄. The fatty acid composition of the plasma membranes was almost identical to that of the microsomal preparation and both membrane fractions exhibited similar rates of the lipid peroxidation that was stimulated non-enzymically by γ-radiation or incubation with ascorbate and iron. The absence of CCl₄-induced lipid peroxidation in the plasma membranes seems to be due, therefore, to an absence of CCl₄ activation rather than an inherent resistance to lipid peroxidation. We conclude that damage to the hepatocyte plasma membrane during CCl₄ intoxication is not due to a significant local activation of CCl₄ to CCl₃· within that membrane.