The discrepancy between ryanodine binding and its effects on the calcium releasing system of the sarcoplasmic reticulum.

: Heavy sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle were reacted in high ionic strength solutions with ryanodine. The effect of this reaction on ATP - and dinitrophenyl phosphate supported calcium uptake and caffeine induced calcium release were studied. At pH 7.0 calcium uptake and caffeine induced calcium release are simultaneous affected by the occupation of 0.5 pmol ryanodine binding sites/mg protein, having an affinity of 0.33 nM-1.