Effects of superoxide dismutase on cholesterol 7 alpha-hydroxylation in swine.

Effects of carbon monoxide, nitrogen, ferricytochrome c and p-hydroxymercuribenzoate were studied on cholesterol 7 alpha-hydroxylase activity of swine hepatic microsomes. The results suggest that a microsomal electron transport system is involved in hepatic microsomal cholesterol 7 alpha-hydroxylation in swine. Cholesterol 7 alpha-hydroxylation is inhibited by superoxide dismutase in the standard assay system containing a NADPH generating system. Superoxide dismutase also inhibited cholesterol 7 alpha-hydroxylation in the system where superoxides were generated by enzymatic or nonenzymatic means in the absence of NADPH-generating system. The current study suggests that superoxide anion may be an important factor in the cholesterol 7 alpha-hydroxylation of swine.