The distribution of collagenase in the rat uterus during postpartum involution. An immunohistochemical study

A monospecific rabbit anti-rat uterus collagenase antibody has been prepared and used to study the distribution of the enzyme in the rat uterus during postpartum involution. Cryostat sections of rat uteri from 24 to 240 hours postpartum were stained by the indirect immunofluorescent method. Nonpregnant rat uterus revelaed positive staining in basement membranes, in endometrial stroma, in perimuscular and in vascular connective tissue. During postpartum involution of the uterus two types of changes in uterine collagenase were observed: (1) variations in the distrubiton of the enzyme, which became selectively localized in the epithelial basement membrane and in the wall of small blood vessels, and (2) variations in the overall intensity of fluorescent staining, which decreased immediately after delivery and slowly increased back to nonpregnant levels in 5 days. The significance of these findings is discussed in relation to the mechanisms of control of collagenase activity in vivo.