Cholesterol and lipid levels in blood and livers of rats fed unsaturated fats

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Abstract
Some facets of the mechanism of poly-unsaturated fatty acids in lowering serum lipid and cholesterol levels in rats were investigated. Rafs were fed up to 12 weeks fat diets which contained either 20% lard or safflower oil (SFO). Intraperitoneal injections of 0.3 mg/dm2 body surface of acetate-l-14c containing 50 [MU]c of activity per milliliter were administered. Five hours later blood and liver samples were removed for determination of lipid and cholesterol content and radioactivities. The blood lipid and cholesterol levels were about 15 and 30% lower, respectively, in rats fed the SFO diet. Total liver lipids and their activities (counts/min per g wet tissue) were appreciably higher after acetate-14C injection in this group on feeding for the prolonged period. The liver cholesterol content decreased in both groups of rats during the period whereas a constant but higher cholesterol specific activity was maintained in SFO than in the lard-fed rats. Thus the lower blood cholesterol levels in these rats cannot be explained as the result of an increasing accumulation in the liver with a resultant inhibition of its formation. Since more cholesterol is appearing as a result of the ingestion of unsaturated fat diets and is not ultimately stored in the tissues, it must be disposed of in some as yet unknown manner.