Effects of Luteinizing Hormonein Vivoandin Vitroon Cholesterol Conversion to Progestins in Rat Corpus Luteum Tissue

Abstract

Ovarian tissue cholesterol, in rats with luteinized ovaries, has been labeled by intravenous injection of cholesterol-7-3H. The effect of luteinizing hormone (LH) in vivo and in vitro on the incorporation of cholesterol-7-3H into progesterone and 20a -hydroxy-pregn-4-en-3-one in these ovaries has been observed. Increased progestin synthesis in vitro resulted from iv administration of LH to rats 30 min. before removing ovaries for incubation, as well as from direct addition of LH to the incubation medium. A corresponding increase was found in circulating progestins after LH administration in vivo. The incorporation of radioactivity from the cholesterol-7-3H increased to approximately the same extent as synthesis of the progestins, so that the specific activities of the progesterone and 20[alpha] -hydroxypregn-4-en-3-one synthesized were essentially the same in tissue stimulated by LH as in unstimulated tissue. It was concluded that LH, in vivo and in vitro, stimulated the conversion of intracellular cholesterol to progestins in rat lutein tissue.