DELTA-5-DESATURATION OF DIHOMOGAMMALINOLENIC ACID (20-3(N-6)) INTO ARACHIDONIC-ACID (20-4(N-6)) BY RAT-LIVER MICROSOMES AND INCORPORATION OF FATTY-ACIDS IN MICROSOME PHOSPHOLIPIDS

Liver microsomes of rats fed an essential fatty acid (EFA)-deficient diet or a commercial balanced diet were used to study the effect of incubation time on the DELTA-5-desaturation of [C-14]dihomogammalinolenic acid (20:3(n - 6)) into arachidonic acid (20:4(n - 6)) and incorporation of the two acids into microsomal phospholipids. The EFA-deficient diet highly increased the desaturation rate of 20:3(n - 6). Incorporation of the formed 20:4(n - 6) into microsomal phospholipids was also increased but at saturating concentration of substrate only. At early times of incubation, the precursor 20:3(n - 6) was rapidly incorporated into phospholipids. Formation and incorporation of 20:4(n - 6) into phospholipids proceeded more progressively. Data suggest that desaturation of 20:3(n - 6) and incorporation of both 20:3(n - 6) and 20:4(n - 6) into phospholipids occur concomitantly and independently.