Methylarginine

N-Methylarginine is an inhibitor of nitric oxide synthase. Chemically, it is a methyl derivative of the amino acid arginine. It is used as a biochemical tool in the study of physiological role of nitric oxide.

The inhibiting effect of N-methylarginine on vasodilation is lower in hypertensive patients than in normal subjects, indicating endothelial dysfunction. The inhibiting effect of N-methylarginine on vasodilation declines progressively with age, but has been restored with vitamin C (except in the oldest subjects).