IMMUNOHISTOCHEMICAL LOCALIZATION OF ACTIVIN-A IN HUMAN ENDOMETRIAL TISSUES DURING THE MENSTRUAL-CYCLE AND IN EARLY-PREGNANCY

Objective: To investigate the possible localization of activin A in hu man endometrial tissue. Methods: Human endometrial tissue was collecte d from 33 patients who were undergoing abdominal hysterectomy. Human d ecidual tissue was collected from 11 patients, who were having a thera peutic abortion. Tissue was fixed in Bouin's solution and made into pa raffin sections. Tissue sections were stained with monoclonal antibodi es against the inhibin/activin alpha- and beta A-subunits and activin A using an avidin-biotin-peroxidase complex technique. Results: No imm unostaining with antibody against the alpha-subunit was observed in th e human endometrium during the menstrual cycle or in the decidua durin g early pregnancy. By contrast, immunostaining for the beta A-subunit and activin A was observed in the cytoplasm of endometrial glands at a ll phases of the menstrual cycle and in the decidua during early pregn ancy. The intensity of immunostaining for the beta A-subunit was stron g during the menstrual phase, became weaker during the early prolifera tive phase, and was intense again at the late proliferative phase. The immunostaining for the beta A-subunit was weak during the early secre tory phase and became very intense toward the midsecretory and late se cretory phases. The intensity of immunostaining for activin A changed during the menstrual cycle and showed a tendency similar to that for b eta A-subunit. The stromal tells were weakly immunoreactive with antib odies against the beta A-subunit and activin A from the menstrual to t he midsecretory phase and became strong in the late secretory phase. I ntense staining for the beta A-subunit and activin A was observed in t he cytoplasm of decidual cells during early pregnancy. Conclusion: Act ivin A, but not inhibins, is localized in the endometrial tissue. The endometrium may be a major source of activin A during the normal menst rual cycle, and the decidua may be one of the sources of activin A. du ring early pregnancy. (C) 1998 by The American College of Obstetrician s and Gynecologists.