GONADOTROPIN STIMULATES OVARIAN RENIN-ANGIOTENSIN SYSTEM IN THE RABBIT

The present study was undertaken to assess the role of ovarian renin-a ngiotensin system (RAS) in the preovulatory cascade induced by gonadot ropin exposure. In the in vitro perfused rabbit ovaries, exposure to h uman chorionic gonadotropin (hCG) enhanced the secretion rate of angio tensin II (Ang II) within 1 h. The secretion rate reached maximal leve ls at 6 h and then declined thereafter. The intrafollicular Ang II con tent and renin-like activity were also significantly increased at 2 an d 4 h after exposure to hCG, compared with control ovaries perfused wi th medium alone. The level of intrafollicular Ang II after hCG exposur e significantly exceeded the concentration of Ang II in an equivalent volume of plasma. The addition of 1 mu M captopril to the perfusate si gnificantly inhibited the secretion rate of Ang II stimulated by hCG; however, captopril affected neither the ovulatory efficiency nor prost aglandin production in ovaries treated with hCG. Captopril significant ly inhibited the resumption of meiosis in the ovulated ova and follicu lar oocytes stimulated by hCG. The administration of 100 mu g Ang II a t 2-h intervals to the perfusate reversed the inhibitory effects of ca ptopril on hCG-induced oocyte maturation. In conclusion, these data in dicate that gonadotropin stimulates renin-like activity and Ang II pro duction in the rabbit ovary. Ovarian renin-angiotensin system may play an important role in the process of oocyte maturation after exposure to gonadotropin.