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

Abstract

Chen Q, Barros H, Floren C-H, Nilsson A. Absorption and incorporation into tissue lipids of ³H-arachidonic- and ^l4C-linoleic acid: effects of ethanol in jejunal tissue cultures and in vivo. Scand J Clin Lab Invest 1994; 54:495-504

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. lOmM 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 (lOOmM) 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 3h. 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.

Key Words:

• arachidonic acid
• ethanol
• ethyl ester
• intestinal absorption
• linoleic acid
• phosphatidylcholine
• phosphatidylethanol
• phosphatidylethanolamine
• phosphatidylinositol
• triacylglycerol