Hyperpolarization and relaxation of arterial smooth muscle caused by nitric oxide derived from the endothelium

Abstract

STIMULATION of the endothelial lining of arteries with acetyl-choline results in the release of a diffusible substance that relaxes and hyperpolarizes the underlying smooth muscle1-9. Nitric oxide (NO) has been a candidate for this substance, termed endothelium-derived relaxing factor10,11. But there are several observations that argue against the involvement of NO in acetylcholine-induced hyperpolarization. First, exogenous NO has no effect on the membrane potential of canine mesenteric arteries7. Second, although haemoglobin (believed to bind and inactivate NO (refs 11-15)) and methylene blue (which prevents the stimulation of guanylate cyclase11-16) inhibit relaxation7,12-14, neither has ..