Vascular nitric oxide system

Vascular nitric oxide system

Endothelial cells and smooth muscle cells are situated in the wall of blood vessels. The tone of the blood vessels depends on factors produced in the endothelium. Nitric oxide (NO) is the molecule involved in the regulation of vasodilation. NO is formed by a complex enzymatic reaction, which is under the influence of different receptors (muscarinic, serotonergic, bradykinin).

Activation of one of these receptors results in an increased intracellular Ca2+ concentration. The Ca2+binds to calmodulin and this complex stimulates the enzyme nitric oxide synthetase (NOS) to become active. NOS converts arginine into NO and citrullin. NO diffuses into the smooth muscle cells and activates guanylate cyclase. This enzyme enables the conversion of GTP into cGMP, which causes smooth muscle relaxation, especially in the walls of the blood vessels.


NO can induce vasodilation by


Serotonin reuptake inhibitors are efficient at