Dopamine metabolism in red blood cells in schizophrenia.

A method was developed for the separation by thin-layer chromatography of 14C-labelled 3-methoxy, 4-hydroxyphenethylamine, 3-hydroxy, 4-methoxyphenethylamine and 3,4-dimethoxyphenethylamine (DMPEA) after incubation of dopamine with catechol-O-methyltransferase (COMT) in lysates of human red blood cells (RBC). 14 C-methyl-S-adenosyl-menthionine was used as the methyl donor. Total COMT activity with noradrenaline or dopamine as substrates, respectively, and the pattern of 14C-methylated metabolites of dopamine were measured in RBC of 47 schizophrenic patients and in 34 control subjects. There were no differences between patients and controls. DMPEA was not formed by RBC in schizophrenic patients (or in controls), a finding which argues against the "pnk spot"/DMPEA hypothesis of schizophrenia. The methods used seem suitable for studies of other human disorders where COMT might be involved.