title: Comparative study on the stimulation of superoxide production in guinea-pig eosinophils by the calcium ionophore A23187.
abstract: The effect of calcium and/or magnesium on O2- production by guinea-pig eosinophils stimulated by the calcium ionophore A23187 was studied in comparison to neutrophils. In the absence of calcium, A23187 did not stimulate O2- production in resting eosinophils and neutrophils, regardless of the presence of extracellular magnesium. The A23187-induced O2- production by both cells increased linearly with extracellular Ca2+ concentrations. However, the concentration of Ca2+ required for maximum O2- production in eosinophils was about 10-times lower than that required of neutrophils. The addition of Mg2+ strongly inhibited O2- production, especially in eosinophils at low Ca2+ concentrations. The intracellular Ca2+ concentration was lower in eosinophils than in neutrophils in the resting state, and the enhancement of the intracellular Ca2+ concentration in response to A23187 was much lower in eosinophils than in neutrophils. The activation of the NADPH-dependent O2(-)-forming enzyme (NADPH oxidase) in eosinophils depended on extracellular calcium, as observed in O2- production. However, the NADPH oxidase activity in the particulate fraction from A23187-stimulated eosinophils was only slightly affected by the addition of divalent cations or EDTA. The compound W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride), a calmodulin antagonist, significantly inhibited O2- production by both cells. On the other hand, the compound H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride), a protein kinase C antagonist, was less effective on O2- production than was W-7. H-7 had little effect on O2- production of eosinophils. These findings suggest that NADPH oxidase might be activated by a smaller Ca2+ concentration through the calmodulin-dependent reaction. This was not observed with protein kinase C, at least in eosinophils.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D004804:Eosinophils / Q000187:drug effects / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000097:blood; D009247:NADH, NADPH Oxidoreductases / Q000097:blood; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D013481:Superoxides / Q000097:blood*
chemical_list: D009097:Multienzyme Complexes; D013481:Superoxides; D000001:Calcimycin; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D008274:Magnesium; D002118:Calcium