Role of the L-arginine/nitric oxide pathway in relaxation of isolated human penile cavernous tissue and circumflex veins.
In human penile corpus cavernosum strips, pre-contracted by noradrenaline, electrical stimulation of nerves evoked non-adrenergic, non-cholinergic (NANC) relaxant responses which could be inhibited by tetrodotoxin 10(-6) M, NG-nitro-L-arginine (L-NNA) 10(-7)-10(-4) M, and oxyhaemoglobin 10(-5) M, but not by methylene blue (MB) 10(-5) M. Acetylcholine-induced relaxations were also inhibited by L-NNA 10(-4) M and oxyhaemoglobin 10(-5) M, but were unaffected by pyrogallol 10(-4) M, MB 10(-5) M, and tetrodotoxin 10(-6) M. MB 5 x 10(-4)-10(-4) M significantly reduced the responses to both electrical stimulation and to acetylcholine. Nitric oxide (NO) 10(-7)-10(-4) M and sodium nitroprusside 10(-9)-10(-4) M caused concentration-dependent relaxations. The NO-induced relaxations were inhibited by oxyhaemoglobin 10(-5) M, and the concentration-response curve for sodium nitroprusside was shifted to the right by MB 10(-5) M. The response to sodium nitroprusside was unaffected by L-NNA 10(-4) M, oxyhaemoglobin 10(-5) M, and pyrogallol 10(-4) M. In circumflex veins, pre-contracted by noradrenaline, no NANC-mediated relaxation was found in response to electrical stimulation; acetylcholine caused endothelium-dependent relaxations, which were insensitive to L-NNA 10(-4) M and oxyhaemoglobin 10(-5) M. NO and sodium nitroprusside caused concentration-dependent relaxations; the concentration-response curves for NO and sodium nitroprusside were shifted to the right by oxyhaemoglobin 10(-5) M. Removal of the endothelium left the NO- and sodium nitroprusside-induced relaxations unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
Kirkeby
H J
HJ
Department of Obstetrics and Gynaecology, Aarhus Kommunehospital, Lund, Sweden.
Svane
D
D
Poulsen
J
J
Tøttrup
A
A
Forman
A
A
Andersson
K E
KE
D000109:Acetylcholine / Q000494:pharmacology; D000527:Alprostadil / Q000494:pharmacology; D001120:Arginine / Q000378:metabolism / Q000502:physiology*; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D010413:Penis / Q000098:blood supply* / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D009599:Nitroprusside; D009569:Nitric Oxide; D014660:Vasoactive Intestinal Peptide; D013779:Tetrodotoxin; D001120:Arginine; D000527:Alprostadil; D000109:Acetylcholine