IMMUNOHISTOCHEMICAL LOCALIZATION OF THE ESTROGEN-RESPONSIVE 110 KDA AND 74 KDA POLYPEPTIDES AND COMPLEMENT COMPONENT C3 IN THE RAT GENITAL-TRACT AFTER ESTROGEN-TREATMENT AND DURING THE ESTROUS-CYCLE

In previous studies we showed that two oestrogen-responsive rat uterin e secretory polypeptides of molecular mass 110 and 74 kDa share sequen ce similarities with the alpha and beta chains of rat complement compo nent C3. Using polyclonal antibodies specific to the 110 kDa polypepti de, the 74 kDa polypeptide and rat serum C3, we studied the localizati on of these proteins in the rat genital tract using an indirect immuno peroxidase technique. The results showed that in oestradiol-treated ra ts immunostaining for the three antigens was heterogeneously distribut ed in the epithelia of the endometrium, cervix and vagina and that the intensity of staining was greater after oestrogen treatment than in c ontrols. In oestradiol-treated immature rats, the immunoreactivity for the 110 kDa and 74 kDa polypeptides was greater in the endometrial an d vaginal epithelia than in the cervical epithelium, whereas immunorea ctivity for C3 was greatest in the vaginal epithelium. In cyclic rats, staining by all three antibodies was seen only during pro-oestrus and oestrus, during which stages the immunostaining for the 110 kDa and 7 4 kDa polypeptides was detected only in the endometrial epithelium, wh ereas immunostaining for C3 was also found in the epithelia of the cer vix and vagina. In general, consecutive sections of these tissues reve aled a close correlation between the immunostaining for the 110 kDa an d 74 kDa polypeptides and C3. However, there were some sections that s howed clear differences in staining, suggesting that more than one C3- related protein species was detected in the female rat reproductive tr act.