Transient appearance of fibrinolytic activity at the epithelium of the rat uterus.

The observation by Todd (1964) of a diffuse fibrinolytic activity related to the human endometrium in its secretory stage initiated a reinvestigation of the development of fibrinolytic activity in the uterus and vagina of the rat using the histochemical fibrin slide technique. In addition to the plasminogen activator known to be related to uterine vessels, in the rat in particular to myometrial arteries, diffuse fibrinolytic activity appeared fleetingly at the endometrial surface epithelium in relation to the oestrous cycle. Endometrial glandular epithelium remained inactive. The fibrinolytic activity of the endometrial epithelium is presumably released during cellular degeneration in the secretory phase. The vaginal epithelium produced fibrinolytic activity at an earlier phase of the ovarian cycle than did the endometrial epithelium.