Conjoint radioenzymatic measurement of catecholamines, their catechol metabolites and DOPA in biological samples

Abstract

An assay is described for the simultaneous determination of dopamine, noradrenaline, adrenaline, dopa, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxyphenyl-ethanol, 3,4-dihydroxymandelic acid and 3,4-dihydroxy-phenylglycol, capable of detecting amounts in the femtomol range. The assay is based on the O-methylation of the catechol moiety utilizing S-[³H-methyl]-adenosyl-l-methionine and a partially purified catechol-O-methyl transferase to form the various O-[³H-methyl]-catechol derivatives. The O-[³H-methyl]-catechol derivatives are purified by thin layer chromatography, solvent partitions and/or ion exchange chromatography. The assay was successfully applied to biological sample. It was possible for the first time, to detect free 3,4-dihydroxy-phenylglycol, free 3,4-dihydroxyphenylethanol and 3,4-dihydroxymandelic acid in a small volume (25μl) of blood plasma of man, rat, dog and rabbit. The conjoint measurement of catecholamines and their catechol metabolites in minute amounts of biological samples may contribute to a more detailed understanding of catecholamine metabolism in the peripheral and central nervous system.