Background: Nitric oxide (NO) is suggested as a mediator involved in the regulation of smooth muscle tone, blood flow, and secretory function of the genitourinary tract and originates from different NO synthase (NOS) isoforms located in endothelial, neuronal, and epithelial structures. The aim of the present study was to determine the location of endothelial and neuronal NOS in the human prostate.
Methods: Histochemical NADPH-diaphorase (NADPH-d) staining, ultrastructural NADPH examination, and NOS immunohistochemistry were performed on histologically verified nonmalignant prostate tissue from normal nonobstructive and hyperplastic obstructive human prostates.
Results: In the prostatic tissue, NADPH-d staining and immunohistochemistry with bNOS antibody revealed the existence of a dense nitrinergic innervation of glandular epithelium, fibromuscular stroma, and blood vessels. NADPH-d reaction in glandular epithelium was not confirmed by ecNOS or bNOS immunohistochemistry. In benign prostatic hyperplasia (BPH), the nitrinergic innervation is reduced. The vascular distribution of ecNOS provides evidence for a segmental differentiation of the NO-mediated vascular regulation.
Conclusions: NO plays an important role in the autonomic innervation of all compartments of prostatic tissue. In obstructive BPH, the nitrinergic innervation is reduced compared to that in normal prostate tissue. Further studies are necessary to elucidate the complex role of NO in the prostate.