GROWTH HORMONE-RELEASING FACTOR STIMULATES MEIOTIC MATURATION IN FOLLICLE-ENCLOSED AND CUMULUS-ENCLOSED RAT OOCYTE

This study was designed in order to assess the possible role of growth hormone-releasing factor (GRF) on oocyte maturation. This effect was analyzed in follicle-enclosed, cumulus-enclosed and denuded oocytes ob tained from immature pregnant mare's serum gonadotropin-treated rats. The addition of GRF to the cultures significantly accelerated maturati on in follicle- and cumulus-enclosed oocytes while no effect was seen on denuded oocytes. Also, the neuropeptide was able to induce maturati on in follicle-enclosed oocytes obtained from immature untreated rats. The GRF action was probably not mediated by the vasoactive intestinal peptide (VIP) receptors since the two hormones had different effects on oocyte maturation and on cAMP production by granulosa cells. In add ition the disappearance of the GRF effect observed in the presence of antibodies anti-GH suggested that GRF required the intermediacy of GH to accomplish its effect on oocyte maturation. Finally, GRF did not af fect meiotic maturation when dbcAMP was added to the cultures. Our res ults demonstrate the ability of GRF to accelerate maturation in oocyte s from both primed and unprimed rats. Since the presence and the invol vement of GRF at the ovarian levels is now well established, the prese nt data strongly suggest an important potential role of GRF in the ova rian physiology.