Total, latent and active collagenase during the course of post-partum involution of the rat uterus. Effect of oestradiol

Abstract

Total, active and latent collagenase activities were determined by direct assay of tissue homogenates. The rate of collagen breakdown during post-partum involution of the rat uterus is correlated with the total activity of collagenase. Both are low at parturition, reach a maximum within 24 h and fall slowly to low values by 5 days post partum. Collagenase apparently participates in collagen breakdown in vivo. Estradiol-17.beta. (100 .mu.g/day, i.p.), which inhibits the breakdown of collagen by 36% during the first 4 days of involution, produces a closely corresponding decrease in total collagenase activity. The effect of estradiol in lowering collagenase activity is not due to alterations in collagen substrate, collagenase kinetic behavior or latent-to-active enzyme conversion. Of the total assayable collagenase, about 35% is fully active and 65% is in a latent form. About 70% of this latent from can be activated by a serine proteinase found, together with collagenase, in the insoluble fraction of uterine homogenates.