title: Effect of the calcium ionophore A23187 on superoxide generation in phorbol ester stimulated human neutrophils.
abstract: The calcium ionophore, A23187, and the tumor-promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), interacted synergistically to elicit an accelerated superoxide production response in human neutrophils. The lag period preceding PMA-induced superoxide generation was decreased in a dose-dependent manner by A23187 at a concentration range from 1.0 X 10(-8) to 1.0 X 10(-5) M. Superoxide production rate, however, was subject to biphasic effects. While the rate was potentiated in a dose-dependent manner at A23187 concentrations below 1.0 X 10(-6) M, inhibitory influences became manifest at higher concentrations. Total superoxide production was subject to inhibitory effects, characterized by a mean inhibitory dose of 1.3 X 10(-6) M. The synergistic interaction of A23187 with PMA is consistent with a role for protein kinase C in neutrophil activation. Inhibition at high A23187 concentrations appeared to result from the effects of elevated intracellular Ca2+ levels on either NADPH oxidase itself, or some step in the transduction process linking protein kinase C to the oxidase complex.
mesh_terms: D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology; D010704:Phorbols / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D010703:Phorbol Esters; D010704:Phorbols; D013481:Superoxides; D015240:Phorbol 12,13-Dibutyrate; D000001:Calcimycin; D007770:L-Lactate Dehydrogenase; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium