HUMAN SEMINAL FLUID CONTAINS SIGNIFICANT QUANTITIES OF PRORENIN - ITSCORRELATION WITH THE SPERM DENSITY

The relevance of the tissue prorenin-renin-angiotensin system (PRAS) t o male reproduction has been suggested by several investigators in the past. Although the presence of angiotensin converting enzyme in semen has been demonstrated, unequivocal evidence for the presence of prore nin and renin in the semen is not yet available. We have used a specif ic immunoradiometric assay based on an antibody directed against the p ro-segment of the prorenin molecule to demonstrate that significant qu antities of prorenin are present in human semen samples. Although seme n is a rich source of proteases and protease inhibitors, the assay use d by us, unlike the usual enzymatic renin assay, is not affected by su ch proteases and their inhibitors. Furthermore, Western blotting data clearly demonstrated that prorenin is present in semen as a 48 kDa pro tein. In a majority of semen samples, the prorenin content was found t o be several fold greater than that measured in EDTA-plasma samples. I nterestingly, the level of prorenin was found to be directly proportio nal to the sperm density in semen samples. Our results suggest that se minal prorenin is produced locally within the male reproductive system , although its exact origin is yet to be defined, that a complete pror enin-renin-angiotensin system exists in human semen and that this syst em may be relevant to sperm function.