Fallopian tubes from ten premenopausal women were collected and examined for the presence of inhibin, activin and its type IIA and IIB receptors (ActRIIA and ActRIIB) in the endosalpinx. Immunocytochemistry demonstrated clear staining for the bA, bB subunits and ActRIIA and ActRIIB that increased in intensity from the isthmus to the ampulla. No staining for the a subunit was observed. Whilst the staining of the bA subunit and ActRIIA was seen in almost every epithelial cell, staining for the bB subunit and ActRIIB was more variable. In situ hybridization and RT-PCR confirmed the presence of mRNA for the bA, bB subunits and ActRIIA and ActRIIB. These results indicated that the epithelium of the uterine tube is able to synthesize activin but not inhibin and has receptors for activin. Activins may thus act as paracrine regulators of tubal epithelial cell function, and embryonic activity may also bind to epithelial receptor and initiate intracellular processes that alter epithelial cell secretions.

The detection of transcripts in sectioned tissue by in situ hybridization is a useful method to localize sites of gene expression during development. This protocol is one that we have modified from Scharen-Wiemers and Gerfin-Moser Histochemistry 100:431-440.