Stimulation of 12-lipoxygenase activity in rat platelets by 17 beta-estradiol.

The effects of estradiol on the endogenous fatty acid (specifically, arachidonic acid) composition of cellular phospholipid fractions and the 12-lipoxygenase activity in rat platelets in vivo were studied. Estradiol had no significant effect on the endogenous fatty acid composition of cellular phospholipid fractions. However, estradiol significantly increased 12-lipoxygenase activity in platelets in a dose-dependent manner. The stimulatory effect of estradiol on platelet lipoxygenase was blocked by the anti-estrogen nafoxidine hydrochloride which was injected simultaneously together with estradiol in vivo, suggesting that the effect in target cells was due directly to estradiol.