GENE-EXPRESSION OF ENDOTHELIN-1, ENDOTHELIN-CONVERTING ENZYME-1, AND ENDOTHELIN RECEPTORS IN HUMAN EPIDIDYMIS

We have previously reported the presence of endothelin-1 (ET-1) and it s receptors in the human testis. In the present study we extended our investigations to human epididymis. The rationale of our study origina ted from the fact that sperm appear to be immotile during their transi t through the epididymis. Hence, it is conceivable that specific facto rs, unknown to date, are present in this organ, capable of inducing sm ooth muscle contractions, thus forcing sperm transport. In this paper it is shown that ET-1 messenger ribonucleic acid and protein are readi ly detectable in the epithelial compartment of the human epididymis, a nd that ET-converting enzyme-1, which converts the precursor pro-ET-1 into the active peptide ET-1, is expressed in the epididymis, thus ind icating an active processing of the prohormone. In addition, two class es of ET receptors were characterized and located in the muscle cells of the epididymis. These receptors correspond, in terms of affinity co nstants and capacity, to the ETA and ETB receptors previously characte rized. These receptors mediate the contractile activity of the epididy mis in vitro, thus suggesting that ET-1 can be responsible of sperm pr ogression through this organ, acting via a paracrine mode of action.