Pharmacologic modulation of the IgE or Ca2+ ionophore A23187 mediated Ca2+ influx, phospholipase activation, and histamine release in rat basophilic leukemia cells.
The stimulation of the rat basophilic leukemia cells (RBL-2H3) mediated either through the IgE receptor or by the Ca2+ ionophore A23187 results in 45Ca2+ influx, phospholipase activation, and histamine release. This study compared in parallel the effects of pharmacological agents on 45Ca2+ influx, phospholipase activation as measured by the release of [14C]-arachidonic acid, and histamine release. Microtubule-depolymerizing agents (demecolcine, colchicine, and vinblastine sulfate) did not affect 45Ca2+ influx, but blocked the IgE- or A23187-mediated [14C]-arachidonic acid and histamine release (e.g., IC50 for vinblastine sulfate = 10 nM). In contrast, a microtubule-stabilizing agent (taxol) blocked the IgE- and A23187-mediated 45Ca2+ influx and [14C]-arachidonic acid and histamine release (IC50 = 20 microM). Microfilament-disrupting agents (cytochalasin B, C, D, and E) enhanced 45Ca2+ influx and [14C]-arachidonic acid and histamine release in the same dose-dependent fashion (e.g., EC50 for cytochalasin B = 0.4 microM). Other pharmacological agents such as a metabolic inhibitor (antimycin A), calmodulin inhibitors (W-7, trifluoperazine, and chlorpromazine), and protease inhibitors (TPCK and TLCK) blocked the IgE- and A23187-mediated 45Ca2+ influx and [14C]-arachidonic acid and histamine release. Therefore, the coupling of Ca2+ influx and the phospholipase activation step requires a functioning microtubule system. Other inhibitors act at sites prior to the Ca2+ influx step in the release process.
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D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001491:Basophils / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D003572:Cytochalasins / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects; D004789:Enzyme Activation; D006636:Histamine Release / Q000187:drug effects*; D007073:Immunoglobulin E / Q000276:immunology; D007942:Leukemia, Experimental / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects; D010740:Phospholipases / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats
D001095:Arachidonic Acids; D002147:Calmodulin; D003572:Cytochalasins; D011480:Protease Inhibitors; C031218:cytochalasin A; D016718:Arachidonic Acid; D007073:Immunoglobulin E; D000001:Calcimycin; D010740:Phospholipases; D002118:Calcium