Specificity studies of leukocytic catecholamine receptors.

Using tritium-labeled dl(+/-)epinephrine, we have extended previous studies demonstrating binding of epinephrine to human leukocytes. We have now further assessed the biological significance of this catecholamine binding by comparing the specificity of binding by human leukocytes with the ability of these compounds to inhibit epinephrine-stimulated adenyl cyclase. Binding is specific for catechols, but does not distinguish between physiologically active and inactive stereo isomers, nor between alpha- and beta-adrenergic agonists. Although 2.5 X 10(-4) M 1(-)DOPA, dopamine, d(+)epinephrine and serotonin failed to stimulate leukocytic adenyl cyclase and prevented adenyl cyclase stimulation by 2.5 X 10(-4) M 1(-)epinephrine, the inhibition of adenyl cyclase by d(+)epinephrine is noncompetitive. This catechol-binding site is clearly not the beta-adrenergic receptor. Its physiological significance, if any, remains to be elucidated.