TRC: Vascular NO 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

Option explanation:

the conversion of arginine to citrullin

the stimulation of the guanylate cyclase enzyme

the stimulation of the muscarinic receptor

the conversion of GTP to GDP

Serotonin reuptake inhibitors are efficient at

Extra info: Despite the theoretical positive effect an increase of serotonin at the synapse would have on vasodilatation, these effects have not been found clinically.

Option explanation:

inducing vasodilatation

increasing circulating calcium ions

decreasing cyclic GMP levels intracellularly

none of the above

Vascular nitric oxide system

Vascular nitric oxide system

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