title: Hydrogen sulfide as a mediator of human corpus cavernosum smooth-muscle relaxation.
abstract: Hydrogen sulfide (H(2)S) is synthesized by 2 enzymes, cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CSE). L-Cysteine (L-Cys) acts as a natural substrate for the synthesis of H(2)S. Human penile tissue possesses both CBS and CSE, and tissue homogenates efficiently convert L-Cys to H(2)S. 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 H(2)S [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/H(2)S pathway mediates human corpus cavernosum smooth-muscle relaxation.
authors.affiliation: Department of Experimental Pharmacology, University of Naples Federico II, Via Domenico Montesano 49, 80131 Naples, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: d'Emmanuele di Villa Bianca
authors.forename: Raffaella
authors.initials: R
authors.lastname: Sorrentino
authors.forename: Pasquale
authors.initials: P
authors.lastname: Maffia
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Mirone
authors.forename: Ciro
authors.initials: C
authors.lastname: Imbimbo
authors.forename: Ferdinando
authors.initials: F
authors.lastname: Fusco
authors.forename: Raffaele
authors.initials: R
authors.lastname: De Palma
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Ignarro
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cirino
mesh_terms: D000818:Animals; D003545:Cysteine / Q000378:metabolism / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006862:Hydrogen Sulfide / Q000494:pharmacology*; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000502:physiology*; D010410:Penile Erection / Q000187:drug effects*; D010413:Penis / Q000502:physiology*; D051381:Rats
chemical_list: D003545:Cysteine; D006862:Hydrogen Sulfide