We previously reported that
activin A, not
inhibin, was localized to endometrial tissues, and that the endometrium might be a major source of
activin A during the menstrual cycle, using an immunohistochemical method. However, there are few detailed reports concerning the expression of
inhibin subunits,
activin receptors and
Smad proteins in the ectopic endometrial tissues of
endometriosis. In this study, our purpose was to evaluate the immunohistochemical localization of
inhibin alpha-, betaA-subunits,
activin A,
activin receptor, and
Smad proteins in ovarian
endometriosis. Tissue samples from ovarian
endometriosis were obtained from 13 women. Normal endometrial tissues were obtained during the proliferative phase from 5 premenopausal women without
endometriosis who were undergoing a
hysterectomy for the treatment of uterine
cervical intraepithelial neoplasia 3. We examined the immunohistochemical localization of
inhibin/
activin alpha-, betaA-subunit,
activin A,
activin receptors types IA, IB, IIA, IIB, Smad2, Smad3 and Smad4 using an
avidin-
biotin-
peroxidase complex technique. No immunostaining for the alpha-subunit of
inhibin was observed in ovarian
endometriosis and the normal endometrium. Positive immunostaining for the betaA-subunit of
inhibin,
activin A,
activin receptors types IA, IB, IIA, IIB, Smad2, Smad3 and Smad4 was observed in ovarian
endometriosis and the normal endometrium. In conclusion, these results suggest that
activin A, but not
inhibins, is produced by ovarian
endometriosis and the normal endometrium, and that the
activin signal transduction system exists in both ovarian
endometriosis and the normal endometrium.