Comparison of cellular mechanisms underlying histamine release from rat mast cells induced by ionic and nonionic radiographic contrast media

Purpose: To determine the cellular mechanisms underlying mast cell histamine release induced by ionic and nonionic radiographic contrast media. Materials and Methods: Histamine release from rat pulmonary mast cells was measured after incubation with various radiographic contrast media. The cellular cAMP content was determined by an enzymatic immunoassay. Results: Both ionic and nonionic contrast media stimulated the histamine release, although the former was more potent than the latter. Dibutyryl cAMP suppressed histamine release evoked by ionic but not nonionic contrast media in a manner dependent on A kinase. The cellular cAMP content was lowered only by ionic contrast media. However, a secretory phospholipase A₂ inhibitor p-bromophenacyl bromide inhibited both ionic and nonionic contrast media-evoked histamine releases. Conclusion: We demonstrated for the first time the difference and similarity in the cellular mechanisms underlying histamine release induced by ionic and nonionic contrast media, in which the reduction in cAMP was specific for ionic materials and the activation of secretory phospholipase A₂ may be common to both agents.