On-line radiochemical assay for monoamine oxidase utilizing high-performance liquid chromatography

A fast and sensitive assay for the determination of monoamine oxidase activity was developed. The method is based on the separation and quantitation of 14C-labeled assay products by high-performance liquid chromatography, which is interfaced directly into a flow-through radioactivity detector. This allows on-line quantitation of the radioactive compounds with picomole sensitivity. The method makes possible the complete separation and detection of the deaminated products of monoamine oxidase A and B substrates benzylamine and 5-hydroxytryptamine, respectively. This assay has been applied to the measurement of monoamine oxidase A and B activities in rat brain.