Similar Ca2+ dependences of [3H]ryanodine binding to α‐ and β‐ryanodine receptors purified from bullfrog skeletal muscle in an isotonic medium

Abstract

To understand the functions of the two ryanodine receptor isoforms (α‐ and β‐RyRs) in nonmammalian skeletal muscles, we determined [³H]ryanodine binding to these isoforms purified from bullfrog skeletal muscle. In 0.17 M‐NaCl medium, both isoforms demonstrated similar Ca²⁺ dependent ryanodine binding activities, while the Ca²⁺ sensitivity for activation of β‐RyR was increased in 1 M‐NaCl medium. This enhancement in Ca²⁺ sensitivity depended on the kind of salts used. These results imply that α‐ and β‐RyRs may have similar properties as Ca²⁺‐induced Ca²⁺ release channels in bullfrog skeletal muscle.