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Hydrogen sulfide as a mediator of human corpus cavernosum smooth-muscle relaxation

By Roberta d'Emmanuele di Villa Bianca, Raffaella Sorrentino, Pasquale Maffia, Vincenzo Mirone, Ciro Imbimbo, Ferdinando Fusco, Raffaele De Palma, Louis J. Ignarro and Giuseppe Cirino


Hydrogen sulfide (H2S) is synthesized by 2 enzymes, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE). l-Cysteine (l-Cys) acts as a natural substrate for the synthesis of H2S. Human penile tissue possesses both CBS and CSE, and tissue homogenates efficiently convert l-Cys to H2S. CBS and CSE are localized in the muscular trabeculae and the smooth-muscle component of the penile artery, whereas CSE but not CBS is also expressed in peripheral nerves. Exogenous H2S [sodium hydrogen sulfide (NaHS)] or l-Cys causes a concentration-dependent relaxation of strips of human corpus cavernosum. l-Cys relaxation is inhibited by the CBS inhibitor, aminoxyacetic acid (AOAA). Electrical field stimulation of human penile tissue, under resting conditions, causes an increase in tension that is significantly potentiated by either propargylglycine (PAG; CSE inhibitor) or AOAA. In rats, NaHS and l-Cys promote penile erection, and the response to l-Cys is blocked by PAG. Our data demonstrate that the l-Cys/H2S pathway mediates human corpus cavernosum smooth-muscle relaxation

Topics: Biological Sciences
Publisher: National Academy of Sciences
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Provided by: PubMed Central
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