Activation and inhibition of the calcium gate of sarcoplasmic reticulum by high-affinity ryanodine binding.
The occupancy of high-affinity ryanodine-binding sites of isolated heavy sarcoplasmic reticulum vesicles occurring in concentrated salt solutions affects ATP-dependent calcium accumulation and caffeine-induced calcium release. The initial suppression of calcium uptake is followed by a marked uptake activation resulting in a reduction of the final calcium level in the medium. Simultaneously, caffeine-induced calcium release is blocked. The dependence of inhibition of calcium uptake and caffeine-induced calcium release observed in assay media containing physiological concentrations of magnesium and ATP on the concentration of ryanodine corresponds to the drug's effectiveness in living muscles.
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D011817:Rabbits; D012433:Ryanodine / Q000494:pharmacology*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*
D000470:Alkaloids; D012433:Ryanodine; D002110:Caffeine; D000255:Adenosine Triphosphate; D002118:Calcium