Cyclic ADP‐ribose induced Ca2+ release in rabbit skeletal muscle sarcoplasmic reticulum

Abstract

The Ca²⁺‐mobilizing metabolite cyclic ADP‐ribose (cADPR) has been shown to release Ca²⁺ from ryanodine‐sensitive stores in many cells. We show that this metabolite at a concentration of 17μM, but not its precursor β‐NAD⁺ nor non‐cyclic ADPR at the same concentration, is active in releasing Ca²⁺ from rabbit skeletal muscle sarcoplasmic reticulum. The release was not sensitive to Ruthenium red (1μM) nor to the ryanodine receptor‐specific scorpion toxin Buthotus ₁‐1 (10 μM). In planar bilayer single channel recordings, concentrations up to 50μM cADPR 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 ryanodine receptors.