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 [14C]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.