A sensitive and rapid fluorimetric assay for monoamine oxidase utilizing high pressure liquid chromatography

A rapid and sensitive assay for the measurement of monoamine oxidase (MAO) activity was developed. This method utilizes high pressure liquid chromatography with fluorescence excitation at 280 nm and detection of 330 nm at pH 5.0 of indoleacetic acid and 5-hydroxyindoleacetic acid, the deaminated products of two substrates for MAO, tryptamine, and serotonin, respectively. The assay allows for the complete separation of metabolites from either of the two substrates. The method has been used to determine MAO activity in the frontal cortex and caudate nucleus of rat brain using tryptamine and serotonin as substrates. The ease and rapidity of this assay make it sutable for use where routine enzyme determinations are required.