title: Hyperoxia alters effect of calcium on rat alveolar macrophage superoxide production.
abstract: The effect of hyperoxia on the Ca2+ dependence of stimulated superoxide anion radical (O2-.) production (the respiratory burst) of rat alveolar macrophages was investigated. Enhancement of the concanavalin A (con A)-stimulated respiratory burst by extracellular Ca2+ was suppressed by O2 exposure. Similarly, the inhibitory effect of verapamil on the con A-stimulated respiratory burst was reduced by O2 exposure. O2 exposure also inhibited con A stimulation that was independent of Ca2+ entry. Exposure to O2 also caused a decline in O2-. production stimulated by either A23187 or phorbol myristate acetate (PMA). With A23187 stimulation, extracellular Ca2+ was essential for either air-exposed (control) or O2-exposed cells. With PMA, stimulation was independent of extracellular Ca2+ for either air or O2-exposed macrophages and verapamil did not inhibit. Free intracellular Ca2+ concentration ([Ca2+]i) was measured in control and O2-exposed alveolar macrophages. Hyperoxic exposure did not alter [Ca2+]i in unstimulated cells. In controls, con A stimulated an immediate increase in [Ca2+]i followed by a rapid decrease and a second rise and fall. The second elevation was suppressed by verapamil or ethyleneglycol-bis (beta-aminoethylether)-N,N'-tetraacetic acid or O2 exposure. The results of both the respiratory burst assays and measurement of con A-stimulated changes in [Ca2+]i suggest that Ca2+ entry involved in stimulus-response coupling is suppressed in cellular O2 toxicity.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D003208:Concanavalin A / Q000494:pharmacology; D066298:In Vitro Techniques; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010100:Oxygen; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D003208:Concanavalin A; D013481:Superoxides; D000001:Calcimycin; D014700:Verapamil; D013755:Tetradecanoylphorbol Acetate; D010100:Oxygen; D002118:Calcium