Elijah B. Romanoff

In vitro inhibition of cholesterol synthesis by pregnenolone in bovine corpus luteum

Abstract Bovine corpus luteum slices and. minces were incubated with acetate-1- 14 C in the presence of pregnenolone. There was a general inhibition in the utilization of acetate-1- 14 C as manifested, by a decreased incorporation of radioactivity into digitonin precipitable sterols, cholesterol, progesterone, and the total lipid extract of the tissue. LH which alone would stimulate the incorporation of acetate-1- 14 C into these substances was not able to reverse the pregnenolone-induced. inhibition. It is suggested that pregnenolone may have a role in the regulation of steroidogenesis in the corpus luteum.

A method for the determination of progesterone in biological specimens

Abstract A method for the analysis of progesterone has been described which combines the isolation of radiochemically pure progesterone with quantitation based on the formation of progesterone-3,20-bisdinitrophenylhydrazone. The method has been developed for the analysis of progesterone in whole blood and tissues.

Electron transport and progesterone biosynthesis in the bovine corpus luteum homogenate

Abstract The role of electron transport in progesterone biosynthesis was investigated in bovine corpus luteum homogenate. Although amytal and malonate inhibited progesterone synthesis, rotenone under several different incubation conditions was without effect. On the basis of differences in the effects of amytal and rotenone it is suggested that for the side-chain cleavage of cholesterol, although formation of some high energy intermediate of oxidative phosphorylation is obligatory, the electron shuttle between NAD and flavin is not.

On the possible site of pregnenolone inhibition of sterol biosynthesis in the bovine corpus luteum

Abstract Bovine corpus luteum homogenates were incubated with acetate1-14C or mevalonic acid-2-14. Pregnenolone was found to inhibit the incorporation of acetate-1-14C but not that of mevaionic acid2-14C into digitonin precipitable sterols. The pregnenolone-induced inhibition could be reversed completely by NADP. Other major steroids of the bovine corpus luteum i.e., progesterone, 20β-hydroxypregn-4-en-3-one and cholesterol were without any effect on acetate-1-14C incorporation into digitonin precipitable sterols. The results indicate that pregnenolone inhibits sterol synthesis before the formation of mevaionic acid.

Cholesterol precursor pools of progesterone in the bovine ovary perfused in vitro.

Summary Bovine ovaries were perfused in vitro with acetate-1-14C throughout an experiment which lasted 377 minutes. Luteal ovaries and the contralateral follicular ovaries were sequentially infused with prolactin, and then with LH. At the end of the perfusion, the specific activity of luteal cholesterol-14C was slightly greater than the specific activity of either the luteal tissue progesterone-14C or the secreted progesterone-14C. The specific activity of the cholesterol-14C isolated from the residual stromal tissue and from the follicular ovaries was much lower than that observed in the corpus luteum.