title: Hydrogen sulphide: a novel endogenous gasotransmitter facilitates erectile function.
abstract: BACKGROUND
  In a pilot study, we found that the novel gasotransmitter, hydrogen sulfide (H2S), had a vasodilatory and proerectile action on the cavernosum. In the present work, we explored the ability of the cavernosum to synthesize H2S and its mechanism on the cavernosal pathways.
  
  
  OBJECTIVE
  To evaluate the physiopharmacological responses and mechanism in the erectile function of H2S in rabbit cavernosum.
  
  
  METHODS
  Rabbit corpus cavernosum (CC) smooth muscle tissue (N = 5) was homogenized and incubated with L-cysteine (10 mM) and pyridoxal 5'-phosphate (2 mM) to detect H2S formation. In isometric tension studies on rabbits (N = 12), the effect of sodium hydrogen sulfide (NaHS; stable H2S donor, 100 microM-3.2 mM) was evaluated on the relaxant and contractile pathways in the cavernous smooth muscle using standard pharmacological tools.
  
  
  METHODS
  In vitro evidences for cavernosal H2S formation and proerectile pharmacological effects.
  
  
  RESULTS
  H2S was readily synthesized in the rabbit CC (2.1 +/- 0.4 nmol/mg protein). In organ bath studies, NaHS consistently relaxed the rabbit CC in a concentration-dependent manner. MDL 12,330A and 1-H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one inhibited the NaHS relaxation by 22.5% and 14.7%, respectively. All three enzyme inhibitors (aminooxyacetic acid [AOAA], beta-cyanoalanine [beta-CA], and DL-propargylglycine [PAG][1 mM]) markedly increased the noradrenergic contractile neurotransmission of CC strips to field stimulation with minimal reversal by cysteine (1 mM) indicating the possible inherent inhibition of the relaxant H2S formation. AOAA, beta-CA, or PAG had no significant effect on nitrergic relaxation of noradrenaline-precontracted CC strips.
  
  
  CONCLUSIONS
  These pioneering studies provide evidence for the endogenous formation of H2S and its proerectile relaxant effect on the cavernosum, with the possibility of involvement of the cyclic adenosine monophosphate pathway.
authors.affiliation: Department of Obstetrics & Gynaecology, National University Hospital, National University of Singapore, Singapore.
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Srilatha
authors.forename: P Ganesan
authors.initials: PG
authors.lastname: Adaikan
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Philip K
authors.initials: PK
authors.lastname: Moore
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006862:Hydrogen Sulfide / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism* / Q000494:pharmacology; D010410:Penile Erection / Q000187:drug effects / Q000502:physiology*; D010413:Penis / Q000187:drug effects; D010865:Pilot Projects; D011817:Rabbits; D014665:Vasodilator Agents / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D018377:Neurotransmitter Agents; D014665:Vasodilator Agents; D006862:Hydrogen Sulfide