Differential Action of Decidual Luteotropin on Luteal and Follicular Production of Testosterone and Estradiol*

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Abstract
Decidual tissue of the rat produces a hormone with physiological and biochemical characteristics similar to those of PRL [prolactin]. Because PRL affects both follicular and luteal production of testosterone and estradiol, it was of interest to determine whether decidual luteotropin affects basal and/or LH [luteinizing hormone]-stimulated ovarian secretion of steroids and whether it differentially affects follicular and luteal synthesis of testosterone and estradiol. The uteri of pseudopregnant adult rats were scratched on day 5 to induce decidual tissue formation. Pseudopregnant animals without decidua were used as controls. Rats were either hypophysectomized on day 8 or left intact. They were treated with 1.5 IU hCG [human chorionic gonadotropin] day or with vehicle between days 8-9. On day 9, blood was obtained from the ovarian vein and both corpora lutea and large antral follicles were isolated and incubated in vitro. The presence of the decidua significantly suppressed both basal and hCG-stimulated ovarian secretion of estradiol, yet enhanced progesterone production. A similar inhibitory effect of decidual tissue on hCG stimulation of testosterone and estradiol was observed in the hypophysectomized rats. When the effect of decidua on follicles and corpora lutea was studied separately, it was found that follicles of rats with decidua produced significantly less testosterone and estradiol than follicles of rats without decidua. hCG administration to either intact or hypophysectomized rats markedly enhanced the follicular capacity to produce these 2 steroids. The degree of hCG stimulation of follicular steroidogenesis was significantly reduced by the presence of decidual tissue. The decidua did not inhibit the in vitro steroidogenic capacity of corpora lutea. Luteal tissue of intact rats with or without decidua produced similar basal amounts of testosterone and estradiol and responded to a hCG challenge with comparable increases in the production of both steroids. After hypophysectomy the responsiveness of corpora lutea to hCG stimulation differed in rats with or without decidual tissue. Whereas luteal cells of rats without decidual tissue gradually lost their responsiveness to hCG stimulation, luteal cells of rats with decidua remained highly responsive to hCG and produced high levels of testosterone and estradiol. Apparently, decidual luteotropin impairs ovarian secretion of estradiol and significantly inhibits the stimulatory effect of hCG on ovarian secretion of testosterone and estradiol. Evidently, decidual luteotropin affects luteal and follicular production of testosterone and estradiol in opposite ways. It inhibits basal and hCG-stimulated steroid synthesis in the follicles while enhancing luteal cell responsiveness to hCG stimulation of testosterone and estradiol.