J. Bergquist et al., DISCOVERY OF ENDOGENOUS CATECHOLAMINES IN LYMPHOCYTES AND EVIDENCE FOR CATECHOLAMINE REGULATION OF LYMPHOCYTE FUNCTION VIA AN AUTOCRINE LOOP, Proceedings of the National Academy of Sciences of the United Statesof America, 91(26), 1994, pp. 12912-12916
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.