Differential effects of hydroxocobalamin on NO-mediated relaxations in rat aorta and anococcygeus muscle.
In rat aortic rings, hydroxocobalamin (10-30 microM) produced concentration-dependent reductions of the relaxant action of nitric oxide (NO) and the endothelium-dependent, NO-mediated, relaxant action of acetylcholine. In anococcygeus muscles, hydroxocobalamin (10-30 microM) reduced but also prolonged, NO-induced relaxations, but had no effect on non-adrenergic, non-cholinergic-mediated relaxations. Hydroxocobalamin had no effect on the NO-independent relaxant action of papaverine in either tissue. It is suggested that hydroxocobalamin sequesters NO by forming nitrosocobalamin. Nitrosocobalamin did not relax aortic rings, but produced a slowly developing and prolonged relaxation of anococcygeus muscles.
Rajanayagam
M A
MA
Department of Pharmacology, University of Melbourne, Victoria, Australia.
Li
C G
CG
Rand
M J
MJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001341:Autonomic Nervous System / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology; D006879:Hydroxocobalamin / Q000031:analogs & derivatives / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology*; D009603:Nitroso Compounds / Q000494:pharmacology; D010208:Papaverine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
D009603:Nitroso Compounds; C079584:nitrosocobalamin; D009569:Nitric Oxide; D010208:Papaverine; D000109:Acetylcholine; D006879:Hydroxocobalamin