Modification by oral contraceptives in rat of 14C acetate incorporation into platelet lipids.

The in vitro incorporation of acetate 14C in platelets lipids was compared in control female rats (Gr. I) to rats treated for 4 days either by an oral contraceptive ethinyl oestradiol + lynestrenol (Gr. II), or by ethinyl oestradiol alone (Gr. III) or lynestrenol alone (Gr. IV). An increase of 43--45% in the incorporation of acetate could be observed in the two groups (II and III) which received ethinyl oestradiol, while the incorporation in group IV was similar to that of the controls. The lipid fractions of which the synthesis was the most considerably stimulated by the oestrogen treatment, were the neutral lipids as separated from the other lipids by TLC. In groups II and III the incorporation in cholesterol and cholesterol esters was increased by 8 fold and by 10 fold in the free fatty acid fraction. In these two groups, even in the phospholipid fractions PS + PI and PE, the radioactivity was significantly increased. The observed effect of the oral contraceptive studied here on platelet lipid synthesis in female rats, appears to be essentially due to the estrogens, since lynestrenol had only minimal effects in that respect.