Studies of the Metabolism of Polyunsaturated Acids by Short-term Experiments

Abstract

Short-term feeding experiments were examined as a method for studying the metabolism of fatty acids. Rats which had been maintained with fat-free diets for 60 days were administered supplements of individual polyunsaturated fatty acids at levels ranging from 50 to 1000 mg/day. Characteristic changes in the fatty acid composition of the liver lipids, which were investigated previously after feeding 40 mg of polyunsaturated fatty acids daily for 60 days to weanling rats, were observed when as little as 50 mg of the same acids were fed for 5 days to adult EFA-deficient rats. An optimal dietary amount of either linoleic acid or linolenic acid, judged by maximal response in the metabolites of these in the liver, was 200 to 400 mg/day/animal. High dietary levels of either linoleic acid or linolenic acid resulted in an apparent decrease in the levels of the metabolites of these in the liver lipids. Norlinoleic acid (17:2ω6) was converted to 19:2ω6 in the tissues but was not dehydrogenated. Dietary linolenic acid was shown to exert an inhibitory effect upon the conversion of arachidonic acid (20:4ω6) to 22:5ω6.