Regulation of inhibin synthesis in the rat ovary.

The lifespan of the female rodent is characterized by dynamic changes in the hormonal regulation of the reproductive axis. From the time ovarian follicular growth is initiated in peripubertal animals, through recruitment, ovulation and luteinization during the estrous cycle, to the quiescent follicular development of pregnancy, and ultimately to follicular exhaustion, tremendous changes in follicular architecture, hormonal responsiveness, steroid secretion, and inhibin and activin synthesis occur. Similar changes in both the biosynthetic functions and hormonal responsiveness of the pituitary are likely to occur. Some of the information on inhibin expression during the reproductive life-span of the rat reviewed here is summarized in a schematic fashion in Figure 3, which presents changes in serum FSH, ovarian inhibin production, and follicular development during different reproductive states. From recent observations regarding ovarian inhibin expression as a function of reproductive status, a partial picture of the complex interactions between steroid and peptide hormones necessary to maintain reproductive cyclicity in mammals is beginning to emerge. Study of the inhibin gene family and of other FSH-regulatory hormones is likely to further enhance our understanding of both normal reproductive processes and of reproductive disorders.