Hormonal regulation of early follicle development in the rat ovary

Although earlier studies focused on the hormonal regulation of antral and p reovulatory follicles, recent studies indicate the importance of the hormon al control mechanism for preantral follicles. The endocrine hormone FSH is not only a survival factor for early antral follicles but also a potent gro wth and differentiation factor for preantral follicles. In addition, KGF se creted by theca cells and c-kit ligand secreted by granulosa cells play par acrine roles in the regulation of preantral follicle growth and development . Furthermore oocyte-derived GDF-9 promotes the growth and differentiation of early follicles by acting on somatic cells in the follicle. It is likely that the genetic makeup of an oocyte could determine the secretion of oocy te hormones which would, in turn, regulate the growth and differentiation o f the surrounding somatic cells of that follicle. A better understanding of the hormonal mechanisms underlying early follicle development could provid e a refined culture system for the in vitro maturation of fertilizable oocy tes and future design of fertility and contraceptive agents. (C) 2000 Elsev ier Science Ireland Ltd. All rights reserved.