Biosynthesis of cholesterol and cholesterol precursors in platelets of female rats treated with oral contraceptives.

Rat platelets were incubated with sodium [U-14C]acetate and labeled lipids were analyzed. The major part of the radioactivity was found in phospholipids and in acylglycerols. When the incubation was performed with platelets of female rats treated with contraceptives, the total incorporation of labeled acetate in lipids was 2-fold higher and 33.6% of the radioactivity was found in lanosterol plus 24-dihydrolanosterol. Moreover, there is labeling of cholesterol. All these compounds were analyzed and identified by gas-liquid chromatography/mass spectrometry. In the incubation with sodium [2-14C]mevalonate the labeling of lanosterol plus 24-dihydrolanosterol and of cholesterol was increased by 30% in platelets of treated rats. The effect of contraceptives on one step of cholesterol biosynthesis is discussed and a possible explanation of the correlation between oral contraceptives and thromboembolic accidents is suggested.