Effect of epinephrine on the oxidative desaturation of fatty acids in the rat adrenal gland.

Delta-6 and delta 5 desaturation activity of rat adrenal gland microsomes was studied to determine the effect of microsomal protein and the substrate saturation curves. This tissue has a very active delta 6 desaturase for linoleic and alpha-linolenic acids. The administration of epinephrine (1 mg/kg body weight) 12 hr before killing, produced approximately a 50% decrease in desaturation of [1-14C]linoleic acid to gamma-linolenic acid, [1-14C]alpha-linolenic acid to octadeca-6,9,12,15-tetraenoic acid and [1-14C]eicosa-8,11,14-trienoic acid to arachidonic acid. A 30% decrease in delta 5 desaturation activity was also shown after 7 hr of epinephrine treatment. The changes on the oxidative desaturation of the same fatty acids in liver microsomes were similar. No changes were observed in the total fatty acid composition of adrenal microsomes 12 hr after epinephrine treatment. Mechanisms of action of the hormone on the biosynthesis of polyunsaturated fatty acids in the adrenal gland are discussed.