Oxidation of cholesterol by rat liver mitochondria: effect of dietary fat

Rats were maintained on normal diets or on diets containing 20 per cent of corn oil (unsaturated, iodine number 127) or commercial shortening (saturated, iodine number 73) for 40 days. The liver mitochondria of the rats fed saturated fat oxidized cholesterol-26-C14 to C1402, to a much greater extent than did liver mitochondria from rata fed unsaturated fat. In general, liver mitochondria from control rats also oxidized more cholesterol-26-C14 than did mitochondria from rats fed unsaturated fat, but this difference was not nearly as consistent (7 of 12 experiments). These results were the same with rats of either sex. Oxidation of sodium pyruvate-2-C14 did not vary with diet. The results could not be attributed to differences in liver lipid or cholesterol content. It has been shown that the homologous combination of liver mitochondria and boiled supernatant from the livers of the unsaturated-fat-fed rats greatly impairs cholesterol oxidation. Addition of boiled supernatant from the other dietary groups to liver mitochondria from the rats fed unsaturated fat restores the cholesterol oxidation to normal levels as does substitution of a 10 per cent sucrose solution for the boiled supernatant. Addition of the boiled liver supernatant from the animals fed unsaturated fat to liver mitochondria from the normal or saturated-fat-fed rats has no appreciable inhibitory effect.