DISTRIBUTION OF NITRIC-OXIDE SYNTHASE IMPLIES A REGULATION OF CIRCULATION, SMOOTH-MUSCLE TONE, AND SECRETORY FUNCTION IN THE HUMAN PROSTATEBY NITRIC-OXIDE

BACKGROUND. Nitric oxide (NO) is suggested as a mediator involved in t he regulation of smooth muscle tone, blood flow, and secretory functio n of the genitourinary tract and originates from different NO synthase (NOS) isoforms located in endothelial, neuronal, and epithelial struc tures. The aim of the present study was to determine the location of e ndothelial and neuronal NOS in the human prostate. METHODS. Histochemi cal NADPH-diaphorase (NADPH-d) staining, ultrastructural NADPH examina tion, and NOS immunohistochemistry were performed on histologically ve rified nonmalignant prostate tissue from normal nonobstructive and hyp erplastic obstructive human prostates. RESULTS. In the prostatic tissu e, NADPH-d staining and immunohistochemistry with bNOS antibody reveal ed the existence of a dense nitrinergic innervation of glandular epith elium, fibromuscular stroma, and blood vessels. NADPH-d reaction in gl andular epithelium was not confirmed by ecNOS or bNOS immunohistochemi stry. In benign prostatic hyperplasia (BPH), the nitrinergic innervati on is reduced. The vascular distribution of ecNOS provides evidence fo r a segmental differentiation of the NO-mediated vascular regulation. CONCLUSIONS. NO plays an important role in the autonomic innervation o f all compartments of prostatic tissue. In obstructive BPH, the nitrin ergic innervation is reduced compared to that in normal prostate tissu e. Further studies are necessary to elucidate the complex role of NO i n the prostate. (C) 1997 Wiley-Liss, Inc.