DISCOVERY OF ENDOGENOUS CATECHOLAMINES IN LYMPHOCYTES AND EVIDENCE FOR CATECHOLAMINE REGULATION OF LYMPHOCYTE FUNCTION VIA AN AUTOCRINE LOOP

Evidence has been obtained that catechol amines and their metabolites are present in single lymphocytes and extracts of T- and B-cell clones by use of capillary electrophoresis with electrochemical detection. P harmacological inhibition of tyrosine hydroxylase reduces observed cat echolamine levels, suggesting catecholamine synthesis by lymphocytes. Intracellular dopamine levels are shown to be increased by extracellul ar dopamine, suggesting a cellular-uptake mechanism. Furthermore, incu bation with either dopamine or L-dihydroxyphenylalanine, a precursor o f dopamine, results in a dose-dependent inhibition of lymphocyte proli feration and differentiation. Together, these results suggest the pres ence of an autocrine loop whereby lymphocytes down-regulate their own activity.