Platelet MAO concentration and molecular activity: II. Comparison of normal and schizophrenic populations

Platelet monoamine oxidase (MAO B) in 59 normal and 57 RDC-diagnosed medicated and unmedicated schizophrenic subjects was analyzed for whole platelet and extracted activities, specific concentration, and molecular activity. A novel radioimmunoassay using a monoclonal antibody elicited to human platelet MAO was used. Female schizophrenics showed no differences from female normals in MAO measures; however, these data could not be clearly evaluated because of confounding effects of age and drugs. Male schizophrenics treated with neuroleptics expressed significantly reduced whole platelet MAO activity, compared to untreated male patients. Compared with normal males, male schizophrenics showed significantly lowered molecular activities, along with elevated specific concentrations, which did not appear to be explained solely by drug usage. Additional mechanisms explaining the diminished molecular activity in male schizophrenics may be the presence of an endogenous irreversible inhibitor or a genetically determined, possibly structural, variant of MAO B.