Endogenous catecholamine synthesis, metabolism, storage, and uptake in human peripheral blood mononuclear cells

Evidence has been obtained that peripheral blood mononuclear cells contain dopamine, norepinephrine, epinephrine, and their metabolites. Pharmacologic inhibition of tyrosine hydroxylase or monoamine oxidase profoundly affecte d intracellular catecholamines (CTs) and their metabolites, indicating that these cells are able to synthesize and breakdown CTs, The sensitivity of i ntracellular CTs to reserpine and the presence of CTs in the extracellular medium suggest that CTs are stored and released. Moreover, the increase of extracellular CTs in the presence of monoamine uptake blockers point to the presence of functional uptake mechanisms. Altogether, these results indica te the existence of a CT lifecycle in human mononuclear cells and warrant f urther studies to investigate the role of adrenergic autoregulatory mechani sms in modulation of the immune response and in the pathogenesis of disease s involving the immune system, (C) 1999 International Society for Experimen tal Hematology. Published by Elsevier Science Inc.