The influence of exogenous cholesterol on the fatty acid composition of liver lipids in the rats given linoleate and γ‐linolenate

Abstract

Abstract Three groups of rats were given cholesterol and cholic acid for four weeks, and then fed a diet with 20% lard (group 1), a diet with 4% of the lard substituted by methyl linoleate (group 2), and a diet with 2% substituted by methyl linoleate and another 2% by methyl γ‐linolenate (group 3) during the same period. Two control groups (4 and 5) received the same diets as did groups 2 and 3, respectively, but without cholesterol and cholic acid. The hepatic cholesterol accumulation was significantly less in group 3 than in groups 1 and 2, and distinct differences in the degree of plasma cholesterol elevation were found among the cholesterol fed groups (1>2>3). Supplement of γ‐linolenate resulted in a reduction of the ratio of arachidonate to homo‐γ‐linolenate in both the cholesterol‐fed group and the control group, but the ratio was much lower in the former. Incorporation of 1‐ 14 C‐linoleate and 1‐ 14 C‐γ‐linolenate into the liver lipids of groups 2 and 4, and groups 3 and 5 was observed respectively at 1 and 3 hr after the intravenous injection. The specific activity of arachidonate from both of the labeled acids in phospholipid and triglyceride was apparently lower in groups 2 and 3 than in groups 4 and 5, respectively. The distribution rate of radioactivities in tetraenoic acids was also low in groups 2 and 3 among the fatty acids of phospholipid and triglyceride. The results indicated impairment of conversion of homo‐γ‐linolenate into arachidonate in the cholesterol‐fed rats.