Selective abolition of sarcoplasmic reticulum vesicles' calcium releasing mechanisms

The ability of calcium loaded heavy sarcoplasmic reticulum vesicles to specifically respond to the addition of various agents such as caffeine, calcium ions and calmodulin antagonists to rapidly released calcium can largely be diminished by passing the vesicular suspension it 0.3 M sucrose, 0.6 M KCl, 4 mM CaCl2, pH 7.0 through a Sepharose 6B column or by centrifuging it through a sucrose gradient prepared with the same salt medium. Inactivation of calcium release does neither interfere with calcium uptake nor with the unspecific releasing effect caused by the application of high concentrations of calmodulin antagonists.