Capacity of Immunologically Purified FSH to Stimulate Cyclic AMP Accumulation and Steroidogenesis in Graafian Follicles and to Induce Ovum Maturation and Ovulation in the Rat

Abstract

Reference preparations of ovine follicle-stimulating hormone (NIH-FSH-S8 and S9; 10-50 .mu.g/ml) induced ovum maturation and stimulated cyclic AMP formation, and as progesterone and 17.beta.-estradiol secretion, by rat Graafian follicles in vitro. These actions of NIH-FSH were retained after immunoabsorption of any contaminating luteinizing hormone (LH) present in the preparations, by treatment with an antiserum to the .beta.-subunit of purified ovine LH (anti-.beta.LH). The corresponding biological actions of NIH-LH-S18 (0.5-10 .mu.g/ml) were abolished by treatment with this anti-.beta.LH serum. A highly purified FSH preparation (64-96 CD, 0.25 .mu.g/ml) also triggered oocytic meiosis and increased follicular progesterone secretion in ivtro. I.p. administration of anti-.beta.LH-treated NIH-FSH-S9 (50 .mu.g/rat at 1430 h) consistently induced ovulation in proestrous rats in which the endogenous gonadotropin surge was blocked by i.p. injection of either Nembutal (1345 h) or antiserum to the LH-releasing hormone (1200 h). Injection (i.p.) of anti-.beta.LH serum on its own into proestrous rats at 1200 h prevented ovum maturation and follicular rupture. Currently available reference preparations of ovine FSH possess the capacity to stimulate follicular adenylate cyclase, steroidogenesis and ovum maturation in vitro, and ovulation in vivo, in the rat, and this capacity cannot be attributed to contamination with material immunochemically identical with LH. It is inferred that the physiological triggering of ovulation and related events in this species depends principally on LH.