Lymphocytes of healthy subjects and schizophrenic patients possess no high-affinity binding sites for spiroperidol

We investigated 3H- and 125I-spiroperidol binding to lymphocytes from healthy subjects and schizophrenic patients and compared it with that to a porcine striatum dopaminergic D2-receptor preparation using identical conditions. Incubation for 60 min at 37 degrees C reduced lymphocyte 3H-spiroperidol binding to 29% of its maximal value. Binding of 3H- and 125I-spiroperidol to striatal membranes was saturable and showed high affinity; the apparent half-maximal saturation constants, KD, were 0.5 nmol/l and 1.0 nmol/l respectively for the two ligands. Lymphocyte membranes did not possess high-affinity binding sites for 3H-spiroperidol; binding to intact lymphocytes was saturable in the micromolar range; the KD values of healthy subjects and schizophrenic patients were similar. Validating all lymphocyte binding studies by parallel experiments with a striatal receptor preparation showed that human lymphocytes do not possess physiologically relevant high-affinity spiroperidol receptors.