Production of activins by the human endosalpinx

Abstract

Uterine tubes from 11 premenopausal and 6 postmenopausal women were collected and examined for the presence of inhibin, activin, and follistatin in the endosalpinx. Immunocytochemistry of tissue from both the isthmic and ampullary regions demonstrated clear staining for the βA- and βB-subunits that increased in intensity from the isthmus to the ampulla. Staining for follistatin showed a similar pattern, but no staining for the α-subunit was observed. Although staining for the βA-subunit was seen in almost every epithelial cell, staining for the βB-subunit was more variable. Western blotting showed a band with an apparent molecular mass of 28 kDa (corresponding to the activin dimer) and a band of approximately 60 kDa (corresponding to the pro-protein of activin). In situ hybridization confirmed the presence of mRNA for the βA- and βB-subunits in the endosalpinx. These results indicate that the endosalpinx is able to synthesize activin, not inhibin, suggesting that in premenopausal women they may have an important role in the biology of the developing embryo. The role in postmenopausal women is less certain, but could lead to the stimulation of FSH secretion by the pituitary gland or other autocrine/paracrine function within the uterine tube.