Effect of Prolactin on Progestin Release and Cholesterol Storage by Rabbit Ovarian Interstitium

Abstract

Previous studies have shown that pituitary luteinizing hormone (LH) accelerates the synthesis and release of 20α-hydroxypregn-4- en-3-one (20α-OH) from rabbit ovarian interstitial tissue (1ST) concomitant with a loss of 1ST cholesterol. When ovarian cholesterol is depleted by a large dose of exogenous LH, steroidogenesis is depressed and less steroid is released. Chronic prolactin treatment promotes cholesterol storage, restores the basal output of 20α-OH and enhances the sensitivity of the ovary to LH in the intact animal. When rabbits are hypophysectomized 24 hr after an iv injection of 250 μg/kg LH, both the IST and the new corpora lutea (CL) become atrophic, cholesterol levels remain low, and no basal release of either 20α-OHor progesterone is detectable. In such animals chronic prolactin treatment causes hypertrophy of the 1ST and elevates cholesterol stores but does not induce progestin release in the absence of estrogen or LH. On the other hand, when the CL are maintained with estrogen, the IST remains atrophic and the basal release of progesterone exceeds that of 20α-OH. If prolactin and estrogen are administered together, both IST and CL hypertrophy and the amount of 20α-OH released is greater than that of progesterone. It can be concluded, therefore, that prolactin acts specifically on the rabbit ovary to maintain the steroid producing capacity as well as the morphology of the IST. (Endocrinology82:122, 1968)