Activin, Inhibin, and Follistatin in Zebrafish Ovary: INTRODUCTION(1)
Activins and inhibins are dimeric proteins belonging to the transforming growth factor p superfamily. Inhibin A and inhibin B are composed of an a subunit and one of the two p subunits, pA and pB, respectively. Activin A and activin B are homodimers of the pA and pB subunits, respectively, while activin AB is the heterodimer of the pA and pB subunits. The in vivo production of these forms of activin has been characterized in mammals. All three forms of activin proteins have also been isolated and purified from Xenopus. Molecular cloning and immunological studies in a variety of animals reveal that these forms of activin may be also present in other lower vertebrates. However, cDNA for a subunit has been cloned from only several mammals, and chickens, but not from lower vertebrates.
Studies in mammals have shown that activins and inhib-ins are involved in many physiological processes, including reproduction. Within the reproductive system, activins and inhibins have been found to regulate the release of GnRH from the hypothalamus and FSH from the pituitary. In addition, activins and inhibins exert many regulatory effects on the testis and ovary, such as steroidogenesis, proliferation of spermatogonia, proliferation of granulosa cells, modulation of FSH receptors, follicle development, and maturation. In most biological systems tested, ac-tivin and inhibin have opposite effects.
Tags: Activin, Inhibin, Oocyte, Zebrafish Ovary