The Role of FSH in the Selection of Large Ovarian Follicles in the Rat

Publisher Website
Google Scholar
Abstract
To determine if the preovulatory FSH [follitropin] surge plays a role in the selection of a cohort of follicles destined to ovulate during the subsequent estrous cycle, exogenous FSH was administered on the day before proestrus and the ovaries were examined 24 h later using histological and morphometric techniques. Administration of exogenous FSH 1 day ahead of the endogenous surge of gonadotropins caused the appearance of a cohort of small pre-Graafian follicles (390-500 .mu.m in diameter) 1 day ahead of the time of their usual appearance. Elimination of the FSH/LH [lutropin] surge on proestrus, by means of a barbiturate blockade of the surge of gonadotropins, prevented the influx of small Pre-Graafin follicles normally seen on estrus. Replacement of FSH in barbiturate blocked animals restored the appearance of these small pre-Graffian follicles. The FSH surge of 1 cycle may rescue follicles in the 200-400 .mu.m size range, thereby selecting those follicles which will ovulate during the next cycle.