title: Drug-induced Ca2+ release from isolated sarcoplasmic reticulum. II. Releases involving a Ca2+-induced Ca2+ release channel.
abstract: Calcium ions that have been preloaded into isolated sarcoplasmic reticulum subfractions in the presence of ATP and pyrophosphate may be released upon addition of a large number of diverse pharmacologic substances. We report here that not only caffeine, but also Ca2+ ions, thymol, quercetin, menthol, halothane, chloroform, 1-ethyl-2-methylbenzimidazole, ryanodine, tetraphenylboron, ketoconazole, miconazole, clotrimazole, W-7, doxorubicin, 5,5'-dithiobis-(2-nitrobenzoic acid), p-chloromercuribenzoic acid, and low concentrations of Ag+ induce Ca2+ release from such triadic sarcoplasmic reticulum. All these drugs induce increased undirectional Ca2+ efflux. We believe all these drug-induced Ca2+ releases are mediated by Ca2+ efflux through the same ion channel since these releases are all greatly attenuated when light sarcoplasmic reticulum is substituted for triads and are even more pronounced when transverse tubule-free terminal cisternae are substituted for triads, and all these forms of drug-induced Ca2+ release are inhibited by submicromolar concentrations of ruthenium red, and by submillimolar concentrations of tetracaine, 9-aminoacridine, and Ba2+, yet they are not affected by nifedipine even at a concentration of 50 microM.
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006221:Halothane / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism*; D008825:Miconazole / Q000494:pharmacology; D011817:Rabbits; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D013748:Tetracaine / Q000494:pharmacology; D013943:Thymol / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D013449:Sulfonamides; D013748:Tetracaine; D012430:Ruthenium Red; D012433:Ryanodine; D002110:Caffeine; D013943:Thymol; C017967:W 7; D008825:Miconazole; D002118:Calcium; D006221:Halothane