Methods. NOS catalytic assay and NOS immunohistochemistry were performed on histologically verified nonmalignant prostate tissue obtained from the peripheral and transition zones of seven radical prostatectomy specimens.

Results. Biochemical analysis revealed NOS activity in the human prostate, with a greater amount in the peripheral zone than in the transition zone (P <0.01). in both prostate zones, NOS was immunohistochemically localized to nerve fibers and ganglia coursing throughout the smooth musculature of the stroma and to subepithelial nerve plexuses. NOS immunoreactivity was also localized to glandular epithelium.

Conclusions. The presence, activity, and distribution of NOS were described in two regions of the human prostate. The present evidence implicates NO in the autonomic innervation and physiology of the human prostate. It is proposed that NO may modulate smooth muscle tone and secretory functions in the human prostate, although functional studies are needed to support these hypotheses.