Platelet monoamine oxidase in a pedigree with schizophrenia: an interlaboratory project

Conflicting reports on the association between platelet MAO activity and schizophrenia prompted a critical review and determinations on identical samples at one laboratory in Sweden and one in the USA. Samples originated from eight schizophrenics and 27 relatives belonging to a large pedigree, thus ensuring biological homogeneity.
In the USA laboratory, a significantly lower MAO activity was found in the schizophrenics when benzylamine or β–phenylethylamine was used as substrate (but not with trypt–amine), while a similar result was obtained in the Swedish laboratory when tryptamine was used (but not with benzylamine or (β–phenylethylamine). Comparisons between materials examined in different laboratories do not seem meaningful until differences in methodologies have been clarified. At present there is neither proof nor disproof of MAO being a "genetic marker" for vulnerability to the schizophrenic disorder.