Absorption and incorporation into tissue lipids of 3H-arachidonic- and 14C-linoleic acid: effects of ethanol in jejunal tissue cultures and in vivo.

Abstract

The effects of ethanol in the rat on the absorption and incorporation of 3H-arachidonic (20: 4, n-6) and 14C-linoleic acid (18:2, n-6) into tissue lipids was examined in jejunal tissue cultures in vivo. The pattern of incorporation earlier seen in the small intestine in vivo, ie. a preferential incorporation of 3H-20: 4 in comparison to 14C-18: 2 into phospholipids (PL), particularly phosphatidylethanolamine (PE) and phosphatidylinositol (PI) was seen in the jejunal tissue cultures. 10 mM ethanol slightly decreased the incorporation of 3H-20: 4 into PE and PI, but did not change the partitioning of labelled fatty acids into phospholipids and triacylglycerols (TG). Ethanol (100 mM) decreased the incorporation of both 3H and 14C into both PL and TG and caused a moderate increase in the TG/PL radioactivity ratio. Rats were also infused intraduodenally with either 10% ethanol or saline and given 3H-20: 4 and 14C-18: 2 in Intralipid. Radioactivity of tissue lipids were analysed after 1, 2 and 3 h. Ethanol did not significantly influence the absorption or the retention in small intestine, liver or heart of 3H or 14C, or the time course for the 3H- and 14C lipid radioactivity in serum. The distribution of 3H and 14C between total nonpolar lipids and individual PLs was also similar in the two groups, 3H-20: 4 thus exhibiting the same preferential incorporation into PLs, compared to 14C-18: 2, in both groups. Significant amounts of 3H and 14C appeared in phosphatidylethanol (PEth) of the small intestine, heart and liver, when the tissues from the ethanol-infused animals were stored frozen before extraction. When the tissues were extracted immediately after the experiment, the proportions of 3H and 14C migrating as PEth did not exceed 0.5%. Although sufficient amounts of ethanol and the phospholipase D activity necessary for PEth formation were thus present in the tissues examined, little PEth formation thus occurred during the ethanol infusion. In the ethanol treated group about 1% of the 3H and 14C radioactivity of the small intestine was in ethyl ester. Intraduodenal infusion of 10% ethanol in vivo thus has little acute effects on the metabolism of absorbed 18: 2 and 20: 4 in the intestinal mucosal cells. Formation of some ethyl ester occurs, however.