Effect of Feeding DL-Ethionine on the Polyunsaturated Fatty Acids of Rat Liver Phospholipids

Abstract

An experiment was carried out to investigate the effect of dietary ethionine on the essential fatty acid composition of rat liver phospholipids. Male and female rats were fed, for 14 days, a 9% casein diet supplemented with either 0.25% DL-ethionine, 0.5% DL-ethionine or 0.25% DL-ethionine plus 0.5% DL-methionine. At the end of the feeding period, livers were removed, their lipids were extracted and separated into triglycerides and phospholipid fractions, and their fatty acids were determined. While ethionine caused variable concentrations of triglyceride in both sexes, it had very little effect on the fatty acid composition of that fraction. Hepatic phospholipid concentrations, however, were much more consistent and similar for both sexes. The percentage of arachidonic acid in this lipid was significantly reduced in both sexes by ethionine, whereas the proportions of linoleic and oleic acids were increased. In both sexes, the largest phospholipid fraction, the phosphatidyl cholines showed the same changes as did the whole phospholipid, but they were more pronounced. The ethionine also decreased the percentage of stearic acid in this fraction, but the change was only significant in females. Only arachidonic acid and a pentaenoic acid were reduced in the phosphatidyl ethanolamines of both sexes by ethionine. Supplementation of the ethionine diet with methionine prevented most of the fatty acid changes in the phospholipid fractions. The results showed, therefore, that dietary ethionine exerts an influence on the metabolism of the phospholipid polyunsaturated fatty acids of both sexes by decreasing the relative amounts of arachidonic acid at the same time that linoleic acid is being increased. Possible reasons for the observed fatty acid changes are discussed.