Agmatine is widely and unequally distributed in rat organs.

We recently discovered' that agmatine, a primary amine generated by decarboxylation of arginine by the enzyme arginine decarboxylase (ADC),2*3 is stored in bovine brain. As such it is the first clonidine-displacing substance (CDS) isolated whose structure has been determined. (See Reis et al., this volume: for a review.) Like clonidine, agmatine binds to imidazoline (I-) receptors of both 11 and Iz subclass and to a2adrenergic receptors.' While prevalent in bacteria, plants, and invertebrates, neither agmatine nor ADC has been considered present in mammalian tissues?v3 Our observation' that brain also expresses ADC indicates that the amine is locally synthesized and is not a product of diet or enteric bacteria. To determine if agmatine is present in rat brain and other organs, we developed a method to allow separation of agmatine from other amines in tissue extracts, permitting its measurement by reversed-phase high pressure liquid chromatography (RP-HPLC). We demonstrate that agmatine is present in this species and widely and unequally distributed throughout the body.