title: Calmodulin participation in oxygen radical-induced cardiac sarcoplasmic reticulum calcium uptake reduction.
abstract: The effect of scavengers of oxygen radicals on canine cardiac sarcoplasmic reticulum (SR) Ca2+ uptake velocity was investigated at pH 6.4, the intracellular pH of the ischemic myocardium. With the generation of oxygen radicals from a xanthine-xanthine oxidase reaction, there was a significant depression of SR Ca2+ uptake velocity. Xanthine alone or xanthine plus denatured xanthine oxidase had no effect on this system. Superoxide dismutase (SOD), a scavenger of .O2-, or denatured SOD had no effect on the depression of Ca2+ uptake velocity induced by the xanthine-xanthine oxidase reaction. However, catalase, which can impair hydroxyl radical (.OH) formation by destroying the precursor H2O2, significantly inhibited the effect of the xanthine-xanthine oxidase reaction. This effect of catalase was enhanced by SOD, but not by denatured SOD. Dimethyl sulfoxide (Me2SO), a known .OH scavenger, completely inhibited the effect of the xanthine-xanthine oxidase reaction. The observed effect of oxygen radicals and radical scavengers was not seen in the calmodulin-depleted SR vesicles. Addition of exogenous calmodulin, however, reproduced the effect of oxygen radicals and the scavengers. The effect of oxygen radicals was enhanced by the calmodulin antagonists (compounds 48/80 and W-7) at concentrations which showed no effect alone on Ca2+ uptake velocity. Taken together, these findings strongly suggest that .OH, but not .O2-, is involved in a mechanism that may cause SR dysfunction, and that the effect of oxygen radicals is calmodulin dependent.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D004285:Dogs; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D019820:Xanthine; D014969:Xanthine Oxidase / Q000378:metabolism; D014970:Xanthines; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D013449:Sulfonamides; D014970:Xanthines; D013481:Superoxides; D019820:Xanthine; D003189:p-Methoxy-N-methylphenethylamine; D004533:Egtazic Acid; C017967:W 7; D014969:Xanthine Oxidase; D002118:Calcium