Effect of Carbon Monoxide on the Relaxtion of the Rabbit Corpus Corpus Cavernosal Smooth Muscle
Korean Journal of Urology (대한비뇨기과학회지)
Korean Journal of Urology (대한비뇨기과학회지), Vol.42(1) : 23~31, 2001
Purpose: Carbon monoxide (CO) is produced during the degradation of hemoglobin to heme (iron protoporphyrin) and biliverdin, and present in various tissues including brain. CO is believed to activate soluble guanylate cyclase to exert its action on the smooth muscles. The effects of CO and its relationships to adrenergic or cholinergic mechanisms were studied using the isolated rabbit corpus cavernosal strips, and the effects of CO and NO were further investigated.Materials and Methods: Using adult New Zealand rabbits, the corpus cavernosal strip was carefully prepared from rabbit penis and was suspended in an 10 ml organ bath containing Tyrode solution. When a stable tension level of the strip had been attained, drugs were added to the organ bath and the change of motility of the strip was recorded on a computerized polygraph. Results: The NO donor, sodium nitroprusside (SNP) and CO caused a dose-dependent relaxation of the cavernosal strip of the rabbit penis. Pretreatment of SNP and CO had no effect on contraction induced by adrenergic drugs and the effects of SNP and CO was not affected by atropine. The relaxation effects of SNP were inhibited by NO scavenger pyrogallol, inhibitor of soluble guanylate cyclase 1H-[1,2,4]oxadiazolo[4,3-a] quinoxalin-1-one (ODQ) and methylene blue. The relaxation effects of CO were significantly inhibited by ODQ and methylene blue. The relaxation effects by acetylcholine were inhibited by NO synthase inhibitor L-nitroarginine methyl ester (NAME) and deendothelialization, but not affected by zinc protoporphyrin (ZnPP), the heme oxidase inhibitor. On the immunostaining of heme oxidase (HO) in corpus cavernosal smooth muscle strip, the positive staining for HO was observed in the perivascular nerve fibers. Conclusions: The relaxation effect of NO was confirmed, and CO exerts an endothelium dependent relaxing effect on the cavernosal strip of the rabbit penis similar to NO. This action is seem to be mediated by soluble guanylate cyclase, and the actions of CO is also mediated by similar guanylate cyclase system.