Basic mechanisms of ovarian endocrine function

Abstract

This review outlines the current understanding of ovarian endocrine development and regulation with both physiological and biochemical background to provide a framework applicable to problems concerning environmental agents and ovarian endocrine function. Two approaches are used. First, the endocrine regulation of foUicle development and corpus luteum function is considered in the classical sense, i.e., viewing these structures as gonadotropin-responsive units undergoing a programmed sequence of development and differentiation. Secondly, a relatively new area of ovarian physiology concerned with intra-ovarian regulation is explored, since this area holds potential for exploration of the direct effects of toxicological or environmental agents upon gonadal endocrine cells. Follicle DevelopmentGonadotropin-Independent and Dependent StagesThe stages of follicular maturation have been classified in a variety of ways by several different investigators, depending upon the degree of detail necessary (1, 2). For purposes of this discussion, distinction need only be made between the following: (1) the primordial follicle stage, characterized by an immature ovum surrounded by a single layer of flattened or disc-shaped granulosa cells; (2) the primary follicle stage, characterized by a transition in granulosa cell morphology to the cuboidal form followed by an increase in the number of granulosa cell layers (In the rat, oocyte growth is complete by the four-layer granulosa cell stage); and (3) Follicle development in most species, with the notable exception of the human (3), is thought to be independent of gonadotropic support up to the

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