title: Quercetin stimulation of calcium release from rabbit skeletal muscle sarcoplasmic reticulum.
abstract: To elucidate the mechanism by which quercetin enhances the rate of tension development in skinned muscle fibers, effects on calcium release from longitudinal tubule-derived SR (LSR) after phosphate-supported calcium uptake were examined. In all studies, 100 microM quercetin (which inhibits initial calcium uptake velocity 85%) was added at or shortly after the time calcium content reached a maximum at various extravesicular Ca2+ concentrations (Cao). At moderate Cao (0.2-1.0 microM), where spontaneous calcium release rate depended on Cao, quercetin caused a marked stimulation of calcium release. This was accompanied by a 60% reduction in calcium influx and a 30-fold increase in calcium efflux. Thus, the previously reported quercetin-induced increase in the rate of tension development by skinned muscle fibers may result, at least in part, from sensitization of Ca2+-triggered calcium release to lower Cao.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology*; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D011794:Quercetin / Q000494:pharmacology*; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D011794:Quercetin; D002118:Calcium