The active uptake of serotonin by platelets of schizophrenic patients and their families: possibility of a genetic marker.

The active uptake of serotonin (5-HT) blood platelets of 20 schizophrenic patients and their families was studied. The uptake was studied over a wide range of 5-HT concentrations (0.1-20 microM), and Km and Vmax of the uptake process were calculated. Of 20 patients, 18 exhibited a lower rate of uptake than the family average at 5-HT concentrations lower than the Km value. At a 5-HT concentration of 0.1 microM, the average 5-HT uptake of patients was 2.15 pmol/10(8) platelets/min, while that of families was 2.99 pmol/10(8) platelets/min (33% difference). At a high 5-HT concentration, only the drug-treated patients had lower Vmax than the family average, and this might be attributed to the effect of the drugs. Km of patients and families were very similar. In eight families, one or more of the family members showed 5-HT uptake patterns very similar to that of the patient. We termed these healthy family members "schizophrenic risks". Our findings indicate the involvement of some genetic factors in this disease.