Serum monoamine oxidase assayed with a new synthetic benzylamine derivative as substrate. Its clinical significance with special reference to hepatic fibrosis.

Serum levels of monoamine oxidase were determined in 171 healthy adults and in 77 patients with hepatic diseases by use of a new synthetic derivative of benzylamine, 1-[(4-aminomethylphenyl)azo]-2-naphthol hydrochloride, as substrate. This new compound is more effectively oxidized by serum monoamine oxidase than by benzylamine, currently the most widely used substrate. Diagnosis of hepatic disease was confirmed in all patients by liver histology. The results suggest that the level of this enzyme in serum increases in parallel with the development of hepatic fibrosis.