Agmatine (decarboxylated l-arginine): Physiological role and therapeutic potential

Agmatine, a cationic amine formed by decarboxylation of l-arginine by the mitochondrial enzyme arginine decarboxylase (ADC), is widely but unevenly distributed in mammalian tissues. Agmatine in the tissues originates from cellular enzymatic de novo synthesis and from agmatine absorbed from the lumen of the gut. Absorption from the gut and accumulation in the tissues and cells must occur via a specific carrier mechanism because the compound is charged at physiologic pH and, hence, biological membranes are almost completely impermeable to the organic cation in the absence of an uptake system. Agmatine initially attracted attention as an endogenous ligand at imidazoline receptors and α2-adrenoceptors. However, independent of binding to those receptors, agmatine induces a variety of physiological and pharmacological effects exhibiting a great therapeutic potential of the compound. Although the precise function of endogenous agmatine is presently still unclear, this review summarizes the current knowledge concerning the physiological and pathophysiological function of agmatine.