Characterization of pannexin1 and pannexin3 and their regulation by androgens in the male reproductive tract of the adult rat.

Pannexins (Panxs) are channel-forming proteins that have homology to the invertebrate gap junction proteins, the innexins. These proteins form membrane channels implicated in ATP release. To evaluate the role of Panxs in the male reproductive tract, we investigated the distribution and regulation of Panx1 and 3 in the testis, efferent ducts (ED), and epididymis of adult rats. In the testis, Panx1 localized to the basal compartment of the seminiferous epithelium, while Panx3 was expressed in Leydig cells. In the ED, both Panxs were expressed in the apical region of ciliated cells. In the epididymis, Panx1 was detected at the base of the epithelium, at times encompassing basal cells, while Panx3 was restricted to the apical plasma membrane of principal cells. Panx3 immunoreactions were high throughout the entire epididymis while Panx1 was high in all regions except the initial segment. Multiple transcripts for Panx1 were identified, and sequence analysis indicated that alternative splicing might account for them. Orchidectomy resulted in the expression of multiple immunoreactive Panx1 bands, and these appeared to be androgen-repressed throughout the epididymis. Panx3 levels in all epididymal regions were also androgen-repressed. Deglycosylation experiments indicated that some Panx1 species were due to glycosylation, but this did not account for all Panx1 immunoreactive species. In summary, Panxs expressed in the epididymis and regulated by both alternative splicing events and androgens. These proteins may play a role in ATP secretion into the epididymal lumen and basal extracellular spaces for functions involving sperm transport and maturation.