[Effect of zinc deficiency on the in vivo biosynthesis of fatty acids of the linoleic series in the rat].

The effect of Zn deficiency on the in vivo synthesis of fatty acids of linoleic acid (n6) series was studied in rat liver. 1-14C Linoleic acid (18:2 n 6), 1-14C acetate plus delta-linolenic acid (18:3 n 6), and 1-14C eicosatrienoic acid (20:3 n 6) were administered to control rats and to animals which had been maintained for 32 days on a Zn-deficient diet. The distribution of label among microsomal fatty acids was measured one hour after the injections. 14C 18:2 n 6 was converted to 14C labeled (n 6) linolenate, eicosatrienoate, arachidonate, and docosapentaenoate. Label from 14C acetate was found in saturated fatty acids and in the above polyenes. The label from 14C 20:3 n 6 was transferred to (n 6) eicosatetraenoate and docosapentaenoate. These results are consistent with the occurrence of active delta 6, delta 5 and delta 4 desaturases, as well as fatty acid elongases in vivo. Zn deficiency modified the fatty acid composition of rat liver microsomes and decreased the rate of conversion of 14C 18:2 to higher homologs. The 20:4 n 6/18:2 n 6 ratio was decreased, which correlated with a decreased production of 14C 20:4 n 6 from 14C 18:2 n 6. The ratio (14C-labeled) phosphatidylcholine/triacylglycerols was significantly decreased in Zn-deprived rats. Zn deficiency thus decreases the activity of fatty acid desaturases and elongases and modifies the activity of the enzymes involved in the incorporation of fatty acids into lipids.