Biosynthesis of estradiol-17 beta fatty acyl esters by microsomes derived from bovine liver and adrenals.

A fatty acyl coenzyme A:estradiol-17 beta acyl transferase activity has been detected in bovine hepatic and adrenocortical microsomes. It is thoroughly increased when adenosine triphosphate (5 mM) and coenzyme A (1 mM) are added to incubation buffer. Using a substrate concentration of 185 microM, the hepatic and adrenocortical microsomal activities have been found to be to 2.4 +/- 0.1 and 5.5 +/- 0.2 nmol/h/mg prot., respectively. Five major estradiol-17-esters have been isolated by reverse phase high performance liquid chromatography from both microsomal incubations, the fatty acid moieties being: arachidonate, linoleate, oleate, palmitate and stearate. However, the distribution of hepatic metabolites is quite different from that obtained with adrenocortical membranes, this is well explained by the corresponding differences between the endogenous contents of free fatty acids. With any of the two types of microsomal membranes used, the results show that estradiol is more susceptible to be esterified to polyunsaturated fatty acids than saturated ones. The possible physiological implications of such an activity in liver and adrenals are discussed.