Serotonin uptake by blood platelets of schizophrenic patients.

Active uptake of serotonin (5-hydroxytryptamine, 5-HT) by blood platelets of acute and chronic schizophrenic patients was compared with that of normal controls. Unlike previous reports, no significant difference in the kinetic parameters (Km and Vmax) of 5-HT uptake between schizophrenic patients and normal controls was observed, although a trend toward decreased Vmax in the acute schizophrenics was present. Since decreased Vmax of platelet 5-HT uptake has been found in patients with bipolar, unipolar, and schizoaffective depression, further study of the usefulness of platelet 5-HT uptake as a biological marker for major depressive illness is indicated. Abnormalities of 5-HT uptake do not appear to contribute significantly to the increased platelet 5-HT levels which have been reported in schizophrenic patients.