Relaxation effect of nitric oxide-donor on diabetic penile smooth muscle in vitro.

The primate model has been used for investigations on the physiology and pharmacology of erection. Recent in vitro investigations indicate that nitric oxide (NO)-donor act as the mediator of penile erection, but it is unclear whether NO-donor could enhance the relaxation effect of sildenafil on diabetic penile smooth muscle. To determine the relaxation effect of NO-donor on diabetic penile smooth muscle, we studied strips of corpus cavernosum tissue obtained from 15 diabetic cynomolgus monkey (Macaca fascicularis). Contraction was induced on isolated strips of corporal smooth muscle by norepinephrine; then relaxation was assessed with the administration of two agents: selective phosphodiesterase type 5 (PDE5) inhibitor (sildenafil citrate) and S-nitroso-N-acetylpenicillamine (SNAP), an NO-donor, and combination of both agents. Analysis of variance was used to compare the responses to the different agents under various treatments. It was concluded that NO-donor could not enhance the relaxation effect of sildenafil on corpus cavernosum of diabetic monkey.