5th February 2024

Nitric oxide

Nitric oxide is a potent vasodilator and is produced by nitric oxide synthase. This is produced from L-arginine and NADPH acting as electron donors. This eventually produces citrulline and nitric oxide. It has a relatively short half-life and acts locally to increase cellular concentrations of cGMP, activating other cellular processes.

Nitric oxide is also produced in other cells, including platelets, macrophages, neutrophils, hepatocytes and smooth muscle cells.

The function of nitric oxide includes:

• Microvascular tone control in organs
• Inhibition of platelet aggregation
• Vasodilation of the systemic circulation
• Neurotransmission
• Immune response is predominantly by phagocytes

Disorders resulting in imbalances in the production or generation of nitric oxide include hepatorenal syndrome, pulmonary hypertension, and CNS cell death.

Medication like nitro-glycerine is directly converted into nitric oxide by the body. Sildenafil acts to increase the levels of cGMP, which nitric oxide is responsible for producing through its action on guanylate cyclase.