Endothelin-1 is synthesized and biologically active in human epididymis via a paracrine mode of action

In a previous study we reported the presence of endothelin-1 and endothelium receptors in the human testis. We hale now extended our investigations to the human epididymis. Since sperm appear to De immotile during, their transit through the epididymis, it is conceivable that specific local factors promote smooth muscle contraction, enabling sperm transport. In this paper the show that endothelin-1 mRNA and protein are readily detectable in the epithelial compartment of the human epididymis, and that endothelin converting enzyme-1, which concerts the precursor pro-endothelin-1 into active endothelin-1, is expressed in the epididymis, consistent with active processing of the prohormone. In addition, two classes of endothelin receptors,were characterized and located in the muscle cells of the epididymis. These receptors correspond, in terms of affinity constants and capacity, to the previously characterized endothelin(A) and endothelin(B) receptor. These receptors appear to De biologically active and mediate the contractile activity of the epididymis in vitro. Our data suggest that endothelin-1, via a paracrine, mode of action, may be responsible for sperm progression through this organ. (C) 1998 by Elsevier Science Inc.