title: The neuronal and endothelium-dependent relaxing responses of human corpus cavernosum under physiological oxygen tension last longer than previously expected.
abstract: BACKGROUND
  Intracavernosal oxygen tension varies greatly in the process of erection. Blood extracted from the human penis demonstrates an increase from approximately 30 mmHg Po(2) in the flaccid state to 100 mmHg in the erect state of the penis. In the present study, using these levels as a guide, we investigate how the NO-dependent relaxation of human corpus cavernosum changed under physiological oxygen tensions ranging from approximately 30 to 100 mmHg.
  
  
  METHODS
  Human penile tissue specimens were obtained at penile surgery with informed consent from the patients. The preparations were mounted in Krebs solution in an organ bath and the isometric tension was recorded. Krebs solutions of various oxygen tensions were prepared by bubbling 5% CO(2) in N(2) and O(2). The NO-dependent relaxation caused by electrical field stimulation (EFS) and acetylcholine (ACh) was studied, and the amplitude and duration of relaxation evaluated.
  
  
  RESULTS
  The amplitude of relaxation induced by EFS was significantly decreased under physiological oxygen tension conditions (P < 0.01). The duration of the relaxant response induced by EFS and ACh was significantly prolonged in physiological oxygen tension conditions than in high oxygen tension (P < 0.01). However, there was no correlation between the duration of relaxation induced by EFS and each physiological oxygen tension level. The duration of relaxation induced by ACh was most prolonged at 60-69 mmHg oxygen tension.
  
  
  CONCLUSIONS
  Physiologically, the effect of NO may last longer than was previously thought. In addition, it would seem that there is an optimal physiological oxygen tension for maximum ACh-induced relaxation.
authors.affiliation: Department of Urology, Takamatsu Red Cross Hospital, Takamatsu City, Japan. nantendo@kln.ne.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kimura
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawanishi
authors.forename: Susumu
authors.initials: S
authors.lastname: Kagawa
mesh_terms: D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology; D000328:Adult; D000368:Aged; D004558:Electric Stimulation; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D010410:Penile Erection / Q000502:physiology; D010413:Penis / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000378:metabolism / Q000494:pharmacology; D014665:Vasodilator Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009569:Nitric Oxide; D000109:Acetylcholine; D011188:Potassium; D010100:Oxygen; D009638:Norepinephrine