Vascular regulation by the L-arginine metabolites, nitric oxide and agmatine.

Research on the biochemistry and physiology of l-arginine has remained an attractive area for scientists over the last 100 years due to its diverse physiological functions in mammals. Research on l-arginine was boosted after the identification of nitric oxide (NO) and agmatine and their physiological importance. NO directly modulates ion channels, activates soluble guanylyl cyclase and other important proteins by ADP ribosylation and nitrosylation and binding to heme or iron-sulfur clusters. These modifications and interaction with heme might activate or inhibit various protein kinases, phosphatases and modulate transcription of various nuclear factors to possibly cause cardiovascular diseases like hypertension, ischemia, diabetes, atherosclerosis and angiogenesis. Agmatine holds the key to prevent the toxic effects associated with induction of NO synthesis by its ability to inhibit inducible nitric oxide synthase (iNOS). Agmatine is also synthesized from l-arginine by the enzyme arginine decarboxylase and displays a significant potential in cardiovascular system. Agmatine, with the myriad of effects on calcium homeostasis, seems to modulate various functions in the heart, brain and vasculature. The present review compiles the recent development to improve the understanding the role played by l-arginine-metabolic pathways in cardiovascular system. Though l-arginine and its metabolites are well known to affect various cardiovascular physiologies, the currently available literature is still not sufficient to validate the prophylactic/therapeutic efficacy of l-arginine. l-Arginine and its metabolites, NO and agmatine still hold the key for future research in cardiovascular system.