The effects of proteolytic enzymes on in vitro ovulation in the rabbit

The involvement of proteolytic enzymes in follicle rupture was assessed by use of the in vitro perfused rabbit ovary. Streptokinase (10 and 100 units/ml) induced ovulation in the absence of gonadotropin. Ovulation failed to occur in contralateral control ovaries. The time of ovulation in streptokinase- and human chorionic gonadotropin-treated ovaries was similar, but significantly more ova from streptokinase-treated ovaries were immature (p < 0.001). Other ovaries were pretreated with trans-4-(aminomethyl)cyclohexane-carboxylic acid, an inhibitor of the conversion of plasminogen to plasmin, and then perfused with human chorionic gonadotropin (50 IU). Ovulatory efficiency was significantly reduced by trans-4-(aminomethyl)-cyclohexane-carboxylic acid at 10 or 1 mmol/L (p < 0.001), but ovum maturity was unaffected. Aprotinin (100 or 10 μg/ml), a potent inhibitor of plasmin, significantly inhibited human chorionic gonadotropin-induced ovulation (p < 0.001) but did not affect oocyte maturation. Scanning electron microscopy of detergent-treated streptokinase-perfused ovaries revealed loosening and decomposition of collagen in the tunica albuginea. These results suggest proteolytic enzyme involvement in follicle rupture.