INHIBITION OF OVULATION IN THE PERFUSED RAT OVARY BY THE SYNTHETIC COLLAGENASE INHIBITOR-SC-44463

A new, powerful, synthetic inhibitor of mammalian tissue collagenases and related metalloproteinases is inhibitory to ovulation in perfused rat ovaries. Ovaries of immature rats, primed with 20 IU of eCG, were dissected and perfused with 0.1-mu-g/ml LH and 0.2 mM 3-isobutyl-1-methylxanthine (IBMX) for 20 h. Addition of SC 44463 (N4-hydroxy-N1-{1S[(4-methoxphenyl)methyl]-2-(methylamino)-2-oxoethyl}-2R-(2-methylpropyl)butane-diamide) at a concentration of 25 nM inhibited ovulation by 55% (9.6 +/- 1.7 ovulations per ovary, mean +/- SEM, compared to a control value of 21.7 +/- 1.7); and 250 nM inhibited ovulation by 75% (5.3 +/- 1.1 ovulations per ovary). We previously showed that the related compound SC 40827 inhibited ovulation by 70% when used at a concentration of 25-mu-M (Brannstrom et al., Endocrinology 1988; 122:1715-1721). We now show that SC 44463 is 100, 500, and 75 times more powerful than SC 40827 in blocking ovulation, inhibiting action of ovarian interstitial collagenase, and inhibiting action of the small metalloproteinase of the rat uterus, respectively. SC 44463 also inhibits ovarian type IV collagen-digesting activity 50% at a concentration of 18 nM. Ovulation occurs after 9-12 h of perfusion with LH. Compound SC 44463 (25 nM) showed its full inhibitory capacity when added to the medium as late as 7 h after LH, but there was no significant inhibition when it was added at 9 h. This suggests that the major collagenolytic events occur beyond 7 h after stimulation by LH.