INCORPORATION OF DELTA-5 DESATURASE SUBSTRATE (DIHOMOGAMMALINOLENIC ACID, 20 3-N-6) AND PRODUCT (ARACHIDONIC-ACID 20/4 N-6) INTO RAT-LIVER CELL-NUCLEI/

The incorporation of [1-C-14]20:3 n-6 and its desaturation product, [1 -C-14]20:4 n-6 into nuclear lipids from rat liver cells were investiga ted during in vitro Delta 5 desaturation. [1-C-14]20:3 n-6 activated a s 20:3 n-6-CoA by nuclear long chain acyl-CoA synthetase was: (1) inco rporated into nuclear lipids mainly esterified to phospholipids and in a lesser proportion, to triglycerides and diglycerides; and (2) desat urated to 20:4 n-6-CoA by the nuclear Delta 5 desaturase. The amount o f [1-C-14]20:4 n-6 acid synthesized in cell nuclei increased along wit h time and was stimulated by the cytosol fraction. The major proportio n of 20:4 n-6 was found in phospholipids and in a lesser proportion it remained as free fatty acids and was esterified to triglycerides and diglycerydes. 20:4 n-6-CoA was incorporated into nuclear lipids and hy drolyzed to free fatty acid. These results indicate that liver cell nu clei possess the necessary enzymes to incorporate the Delta 5 desatura se substrate (20:3 n-6) as well as the product of desaturation (20:4 n -6) into nuclear TG, DG and PL following an acyl-CoA dependent pathway .