Determination of platelet monoamine oxidase by new continuous spectrophotometric method

A simple, continuous spectrophotometric method for the determination of tissue monoamine oxidase based on the oxidation of 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) using peroxidase has already been described (Ivanović, I. & Majkić-Singh, N. (1986) Fresenius Z. Anal. Chem. 324, 307). In the present study the method is optimised for platelet monoamine oxidase assay and applied to healthy persons and schizophrenic patients. The obtained data were statistically analysed. The continuous ABTS method is sensitive, precise (CV below 6.9%) and linear up to 83 U/g protein. Comparison with the end-point method of Szutowicz et al. (1984) Anal. Biochem. 138, 86-94) gave a good correlation (r = 0.983). The reference values for the activity of human platelet monoamine oxidase by the new continuous ABTS method are 25 to 42 U/g protein (means = 33.2 U/g protein, CV = 15.5%, n = 67). No differences were found between females and males, or between three age groups ranging from 21 to 52 years. The patients with chronic (n = 76) or acute (n = 17) schizophrenia had significantly lower monoamine oxidase activities compared with normal values (p less than 0.005), which indicates that platelet monoamine oxidase can be a possible marker for schizophrenic diseases.