Receptors for gonadotropin releasing hormone are present in rat oocytes

Specific receptors for gonadotropin releasing hormone (GnRH) in the rat oocyte have been identified by using two independent methods. Light microscopic autoradiography, utilizing an iodinated biologically active photoaffinity derivative of GnRH, revealed specific binding of the neurohormone to rat oocytes. Furthermore, the presence of GnRH-receptor is also evident from indirect fluorescent immunocytochemistry that shows binding of GnRH-receptor antibodies to rat oocytes which is neither detected with non immune serum nor with antiserum depleted of GnRH-receptor antibodies. These antibodies to the GnRH-receptor, also bind to both cumulus and granulosa cells but not to rat basophilic leukemia cells. The presence of specific GnRH receptors on rat oocytes provides an experimental basis for understanding the molecular events involved in GnRH-induced oocyte maturation.