NITRIC-OXIDE SYNTHASE ACTIVITY IN THE HUMAN UROGENITAL TRACT

Nitric oxide (NO) has been suggested as a nonadrenergic non-cholinergi c neurotransmitter in the urogenital tract and has previously been sho wn to have a smooth muscle relaxing effect in the urogenital organs bo th in various animals and in humans. It has been shown that NO is a me diator of the erection and the dilatation of the bladder neck and uret hra. The aim of the study was to analyse nitric oxide synthase (NOS) a ctivity in the human urogenital tract. NOS activity was measured by th e conversion of L-[U-C-14] arginine to L-[U-C-14] citrulline. In the u pper urinary tract there was Ca2+-dependent NOS activity in the renal pelvis, but no significant NOS activity could be found in the ureter. In the lower urinary tract we found high Ca2+-dependent NOS activity i n the urethra, intermediate activity in the bladder neck and comparati vely low activity in the detrusor muscle. In the male genital tract th e testis and epididymis had no significant NOS activity. The vas defer ens, prostate, seminal vesicle and corpus cavernosum were found to hav e high levels of Ca2+-dependent NOS activity. Ca2+-independent NOS act ivity was not obtained in the urogenital tract. Our results correspond well with previous functional studies indicating NO to be an importan t nerve-induced mediator of erection and in the micturition reflex, bu t also suggest that NO may be involved in several other functions in t he human urogenital tract.