Effect of Gonadotropins on Steroidogenesis in Rat Ovaries at Dioestrus

Abstract

MAINLY because of the classical work of Evans et al.¹ and Astwood², it has been generally accepted that prolactin plays a leading part in the regulation of the function of the corpus luteum in the rat. It has been reported³, however, that prolactin is not capable of acting alone in hypophysectomized rats but requires the synergistic action of a hormone with luteinizing hormone (LH) activity. In all these studies, corpus luteum function or, specifically progestin secretion was assessed indirectly either by the production of traumatic uterine placentomata^1,3 or by the production of persistent vaginal mucification². It is possible to assess progestin secretion directly by cannulating the ovarian vein and measuring the steroids chemically, and by this technique in rabbits it has been found that the intravenous injection of LH produces a rapid and marked elevation of the ovarian secretion of progestins⁴. Prolactin and other pituitary tropic hormones were completely ineffective. The demonstration that the ovarian vein of the rat can be cannulated⁵ afforded us an opportunity to assess the acute effect of tropic hormones on the ovarian secretion of progestin in that animal. This note describes some of the preliminary results.