A sensitive radioenzymatic procedure for the simultaneous determination of dihydroxymandelic acid, dihydroxyphenylglycol, and dihydroxyphenylacetic acid has been developed. The catechols were methylated by catechol-O-methyltransferase using S-adenosyl[methyl-3H]methionine as methyl donor. The assay involved extraction into organic solvent, thin-layer chromatography and periodate oxidation. The applicability of the procedure was tested by measuring the amounts of deaminated metabolites of noradrenaline, adrenaline and dopamine in heart perfusion samples and plasma of rabbits.
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