1. From: Nitric Oxide: A Physiologic Messenger
Ann Intern Med. 1994;120(3): doi: /
Figure Legend:
Nitric oxide arterial smooth muscle.A messenger molecule such as acetylcholine binds to the acetylcholine receptor on an endothelial cell, activating inward calcium currents. Calcium binds to calmodulin and activates endothelial cell nitric oxide synthase, which converts arginine plus oxygen into citrulline and nitric oxide. Nitric oxide diffuses out of the endothelial cell into an adjacent smooth muscle cell and activates guanylate cyclase by binding to the iron in its heme group. The increase in cyclic guanosine monophosphate (cGMP) causes smooth muscle relaxation, and thus vasodilation. GTP = guanosine triphosphate.
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