Dopamine inhibition of superoxide anion production by polymorphonuclear leukocytes

To examine the modulatory effects of catecholamines on the respiratory burst in polymorphonuclear leukocytes (PMNs), dopamine was tested for its capacity to modify the superoxide anion (O2-) production by PMNs under their stimulation with several stimuli. Dopamine inhibited the O2- production by PMNs when PMNs were stimulated with N-formylated chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol myristate acetate, or opsonized zymosan, whereas dopamine did not alter the PMN mobility. The values of percentage inhibition of the O2- production by FMLP-stimulated PMNs were 57% under treatment with 10(-5) mol/L and 83% with 10(-4) mol/L of dopamine. Isoproterenol also inhibited PMN O2- production in response to FMLP. Although a beta-adrenergic blockade, propranolol, diminished the isoproterenol-induced inhibition of the O2- production, it did not affect the inhibitory effect of dopamine. The increase in intracellular cyclic AMP levels in dopamine-treated PMNs was much smaller than the increase in isoproterenol-treated cells. Furthermore, dopamine inhibited the reduced nicotinamide-adenine dinucleotide phosphate-dependent O2- production by subcellular particles. These results indicate that dopamine inhibits PMN O2- production through its effect on PMN reduced nicotinamide-adenine dinucleotide phosphate-oxidase system rather than through its beta-adrenergic action.