EVIDENCE FOR PRODUCTION AND FUNCTIONAL-ACTIVITY OF NITRIC-OXIDE IN SEMINIFEROUS TUBULES AND BLOOD-VESSELS OF THE HUMAN TESTIS

Previous studies have demonstrated that nitric oxide (NO) influences L eydig cell function. Here we provide evidence for NO production and ac tivity in seminiferous tubules and blood vessels of the human testis. By immunohistochemistry, the soluble guanylyl cyclase (sGC), the intra cellular NO receptor, and the second messenger, cyclic guanosine monop hosphate (cGMP), were detected in myofibroblasts of the peritubular la mina propria in Sertoli cells, as well as in endothelial and smooth mu scle cells of testicular blood vessels. Performed with isolated tubule s and blood vessels, the biological activity of sGC could be proved by cGMP generation in response to treatments with the NO donor, sodium n itroprusside. The endothelial and neuronal subtypes of NO synthase (NO S) were localized immunohistochemically to the same cell types that ex press sGC and cGMP. in isolated tubules and vessels, the presence of e ndothelial NOS and neuronal NOS was confirmed by immunoblotting, and N OS activity was demonstrated by decreased cGMP production upon incubat ion with the NOS inhibitor L-nitro arginine methylester. These finding s show that peritubular cells, Sertoli cells, and testicular blood ves sels may be sites of NO production and activity, possibly involved in relaxation of seminiferous tubules and blood vessels to modulate sperm transport and testicular blood now, respectively.