DIRECT OVARIAN EFFECT OF GROWTH-HORMONE IN THE RABBIT

PROBLEM: This study was undertaken to assess whether growth hormone (G H) can stimulate follicle growth and ovarian steroidogenesis via putat ive GH receptors. METHOD: In vitro perfused rabbit ovary. RESULTS: Ovu lation occurred in neither the control ovaries nor experimental ovarie s treated with 100 ng/ml of GH, whereas all ovaries exposed to 50 IU o f human chorionic gonadotropin (hCG) ovulated. The addition of GH to t he perfusate significantly stimulated the follicle growth in the absen ce of gonadotropin. The percent change in follicle diameter in OH-trea ted ovaries did not differ significantly from that in hCo-treated ovar ies. Exposure to GH significantly stimulated the meiotic maturation in the follicular oocytes, as compared with the contralateral control ov aries. Although the concentration of progesterone in the perfusate did not differ significantly between GH-treated and control ovaries, GH s timulated estradiol production by the perfused rabbit ovaries. Rabbit ovary membranes exhibited high affinity binding sites of hGH (Kd = 6.1 x 10(-9)M). CONCLUSION: GH acts on the rabbit ovary to stimulate the follicle growth, oocyte maturation, and ovarian estradiol production b y interacting with the specific receptors located in ovarian plasma me mbranes.