Mechanisms underlying endothelium-dependent, nitric oxide/prostacyclin-independent, acetylcholine-induced relaxation in canine corpus cavernosum.
The mechanisms underlying endothelium-dependent and nitric oxide (NO)/prostacyclin-independent, acetylcholine-induced relaxation in isolated canine corpus cavernosum were investigated. In isolated canine corpus cavernous strips treated with indomethacin (10(-6) M) and N(G)-nitro-L-arginine (10(-4) M), acetylcholine produced relaxations in a concentration-dependent manner. The relaxations were not affected by treatment with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide, sodium salt (carboxy PTIO, 3 x 10(-4) M), glibenclamide (10(-6) M), iberiotoxin (10(-7) M) or charybdotoxin (10(-7) M), but were abolished or reversed to contractions by treatment with apamin (10(-8) M) or scyllatoxin (10(-8) M). Levcromakalim (10(-7)-10(-6) M) induced a concentration-dependent relaxation which was abolished by treatment with glibenclamide (10(-6) M), but was not affected by treatment with apamin (10(-8) M) or scyllatoxin (10(-8) M). These findings indicate that endothelial cells of canine corpus cavernosum have an ability to produce a relaxing substance(s) other than NO or prostacyclin in response to acetylcholine. The substance(s) may open solely small conductance Ca2+-dependent K+ channels.
Ayajiki
K
K
Department of Pharmacology, Shiga University of Medical Science, Ohtsu, Japan.
Fujioka
H
H
Okamura
T
T
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000502:physiology*; D011464:Epoprostenol / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009569:Nitric Oxide / Q000502:physiology*; D019335:Nitroarginine / Q000494:pharmacology; D010413:Penis / Q000187:drug effects* / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology
D015221:Potassium Channels; D019335:Nitroarginine; D009569:Nitric Oxide; D011464:Epoprostenol; D000109:Acetylcholine; D002118:Calcium