CYCLIC ADP-RIBOSE INDUCED CA2-MUSCLE SARCOPLASMIC-RETICULUM( RELEASE IN RABBIT SKELETAL)

The Ca2+-mobilizing metabolite cyclic ADP-ribose (cADPR) has been show n to release Ca2+ from ryanodine-sensitive stores in many cells. We sh ow that this metabolite at a concentration of 17 muM, but not its prec ursor beta-NAD+ nor non-cyclic ADPR at the same concentration, is acti ve in releasing Ca2+ from rabbit skeletal muscle sarcoplasmic reticulu m. The release was not sensitive to Ruthenium red (1 muM) nor to the r yanodine receptor-specific scorpion toxin Buthotus(I)-1 (10 muM). In p lanar bilayer single channel recordings, concentrations up to 50 muM c ADPR did not increase the open probability of Ruthenium red and toxin- sensitive Ca2+ release channels. Thus Ca2+ release induced by cADPR in skeletal muscle sarcoplasmic reticulum may not involve opening of rya nodine receptors.