DETERMINATION OF AGMATINE IN BRAIN AND PLASMA USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

Decarboxylated arginine, agmatine, is a neurotransmitter candidate for imidazoline receptors. A method is described to measure agmatine in r at brain and human plasma by isocratic high-performance liquid chromat ography (HPLC) with fluorescence detection and o-phthalaldehyde deriva tization. Quantitation is based on the method of additions of internal agmatine spikes. This assay has sensitivity in the low picomole range and a detection limit of 100 fmol. The correlation coefficient for th e agmatine standard curve was 0.999+/-0.001 S.D., and intra- and inter -assay C.V.s were less than 8%. The accuracy of our isocratic method c ompared favorably with a gradient HPLC protocol, originally developed for bacterial agmatine, which we modified for use with tissues. Agmati ne concentrations in rat brain were proportioned similarly to the regi onal distribution of imidazoline-l receptors. These methods can be use d as reliable research tools in various biological samples.