Effect of copper and plastic intra-uterine devices on the fibrinolytic activity of the endometrium in the rat.

The effect of copper and plastic intrauterine devices (IUD) on the fibrinolytic activity of the endometrium was studied in the rat. A copper or a plastic device was placed in one of the uterine horns, while the other horn served as a control. Biopsy specimens were obtained from both horns and examined histochemically. The copper concentration was determined by atomic absorption spectroscopy. The fibrinolytic activity of the control horn was found to be localized to small vessels in the outer layer of the uterine wall, while that of the endometrium was low. Plastic as well as copper IUDs increased the fibrinolytic activity which, in contrast with what was seen in the controls, was localized to the endometrium. Compared with the effect of the plastic device, the increase in the fibrinolytic activity induced by the copper device was more widespread in the endometrial area and was accompanied by an increase in the concentration of copper. These findings might help to explain why the contraceptive effect of IUDs is more reliable when they are partly coated with copper.