Stimulation of Progesterone Biosynthesis in Bovine Corpora Lutea by Luteinizing Hormone in the Presence of an Inhibitor of Cholesterol Synthesis1

Slices of corpora lutea from 4 normally cycling dairy cows have been incubated in the absence and in the presence of trans-1,4-bis(2-chlorobenzylaminomethyl) cyclohexane dihydrochloride (AY9944), an inhibitor of cholesterol biosynthesis. AY9944 (10−5M) decreased the in vitroincorporation of acetate-1-14C into cholesterol both in the absence and presence of LH, to 26 and 18% of control rates, in half-hour and 2-hour incubations, respectively. LH was equally effective in increasing the rate of net in vitroprogesterone synthesis in the presence of AY9944 as in its absence. No evidence of a stimulatory action of LH upon cholesterol synthesis was observed; in fact, LH decreased markedly, the incorporation of acetate-1-14C into cholesterol. Neither LH nor AY9944 influenced incorporation of acetate-1-14C into fatty acids of triglycerides or of phospholipids. The ability of LH to increase rate of in vitroglycolysis in this tissue was not affected by AY9944. It is concluded that a stimulation, by LH, of in vitrosynthesis of progesterone in bovine corpus luteum slices does not depend upon rate of concurrent synthesis of cholesterol, and that LH, in addition to stimulating conversion of cholesterol to progesterone, may exert an inhibitory action on cholesterol biosynthesis.