EFFECT OF ESTRADIOL AND TESTOSTERONE ON THE FATTY ACIDS OF PLASMA CHOLESTERYL ESTERS AND PHOSPHOLIPIDS IN THE CASTRATED RAT

Abstract

The effects of physiological doses of estradiol and testosterone on plasma cholesteryl ester and phospholipid fatty acid composition were investigated in castrated male rats. The animals were killed after 3 weeks on experiment, and their plasma cholesteryl esters and phospholipids were analyzed and compared with those of intact female and male rats.Estradiol appeared to be responsible for the increased proportion of plasma cholesteryl arachidonate seen in the female or estrogen-injected rats since the proportion of cholesteryl arachidonate in castrated control rats was lower and similar to that of male or testosterone-treated rats. Plasma phospholipids of female and estradiol-injected rats had a higher percentage of stearic acid relative to palmitic acid. On the other hand, male, castrated control and testosterone-treated rats had higher proportions of palmitic acid. Fractionation of the plasma phospholipids into cephalins, lecithins, sphingomyelins, and lysolecithins, and analyses of their fatty acids, revealed that a principal effect of estradiol was to increase proportions and amounts of stearic and arachidonic acids in the lecithin fraction.The results suggest that estradiol may influence the synthesis of a lecithin rich in stearic and arachidonic acid. A possible relationship between the arachidonic-acid-rich lecithin and the higher percentage of cholesteryl arachidonate in estradiol-treated rats is discussed.