Differential effects of hydroxocobalamin on NO‐mediated relaxations in rat aorta and anococcygeus muscle

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Abstract
In rat aortic rings, hydroxocobalamin (10–30 μm) 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 μm) 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.