The inositol 1,4,5-trisphosphate-forming agonist histamine activates a ryanodine-sensitive Ca2+ release mechanism in bovine adrenal chromaffin cells.
The role of a Ca(2+)-induced Ca2+ release (CICR) mechanism in the generation of agonist-induced increases of intracellular free Ca2+ concentration ([Ca2+]i) was studied in bovine adrenal chromaffin cells. In single cells, repetitive stimulations with caffeine at 200-s intervals evoked reproducible spikes of [Ca2+]i. Ryanodine, an agent that interacts with the CICR channel of muscle, inhibited the caffeine-induced spikes of [Ca2+]i in a "use-dependent" way. High affinity binding sites for [3H]ryanodine (Kd 3.3 nM, Bmax 26 fmol/mg protein) were also detected in membranes from chromaffin cells, supporting the presence of a caffeine- and ryanodine-sensitive CICR channel. Pretreatment of single cells with caffeine + ryanodine to reduce the size of the caffeine-sensitive Ca2+ compartment inhibited a subsequent spike of [Ca2+]i evoked by histamine, a D-myo-inositol 1,4,5-trisphosphate-forming agonist. This demonstrates that a significant portion of the Ca2+ released by histamine comes from a caffeine- and ryanodine-sensitive pool. Ryanodine inhibited by 50% the size of [Ca2+]i spikes evoked by repetitive stimulation with histamine and did so in a use-dependent manner. These data suggest that, in addition to D-myoinositol 1,4,5-trisphosphate, activation of a caffeine- and ryanodine-sensitive CICR channel participates in the generation of histamine-induced release of intracellular Ca2+.
Stauderman
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Marion Merrell Dow Research Institute, Cincinnati, Ohio 45215.
Murawsky
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D000200:Action Potentials; D000818:Animals; D001665:Binding Sites; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002837:Chromaffin Granules / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D006632:Histamine / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology*
D012433:Ryanodine; D002110:Caffeine; D006632:Histamine; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium