Impaired Neurogenic and Endothelium-Mediated Relaxation of Penile Smooth Muscle from Diabetic Men with Impotence

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Abstract
Relaxation of the smooth muscle of the corpora cavernosa of the penis is necessary for penile erection. To determine the relation of impaired relaxation to impotence in diabetic patients, we performed an in vitro examination of corpus cavernosum tissue obtained at the time of implantation of a penile prosthesis in 21 diabetic and 42 nondiabetic men with impotence. Contraction was induced in isolated strips of corporal smooth muscle by norepinephrine; then relaxation was assessed with electrical stimulation of autonomie nerves and with the administration of three agents: acetylcholine, which is known to be mediated by endothelium-derived relaxing factor; papaverine; and sodium nitroprusside. The latter two act directly on smooth muscle (i.e., they are endothelium-independent).