Involvement of Mg2+ in terminating Ca2+ release in cultured rat skeletal muscle

[摘要]

Combined patch-clamp and fura-2 measurements were performed to investigate the mechanism that terminates Ca²⁺ release in rat skeletal myoballs. When cells were intracellularly perfused with solution containing 1 mM free Mg²⁺, the caffeine (10 mM)-induced Ca²⁺ transient was abruptly terminated by membrane repolarization (−70 mV). With low intracellular Mg²⁺ (e.g. 50 μM) perfusion, however, repolarization failed to terminate the caffeine transient. The results show that intracellular Mg²⁺ is necessary for repolarization-induced closing of the Ca²⁺ release channel.

[学科分类] 生物化学/生物物理

[关键词] Skeletal muscle;Excitation-contraction coupling;Ryanodine receptor;Ca2+ release channel;Caffeine;Fura-2;SR;sarcoplasmic reticulum;T-tubule;transverse tubule;RyR;ryanodine receptor;RISC;repolarization-induced stop of caffeine-induced Ca2+ release;DHPR;dihydropyridine receptor;TTX;tetrodotoxin;EGTA;ethylene-glycol-bis-N;N;N′;N′ tetraacetic acid;HEPES;N-2-hydroxyethyl-piperazine-N′-2-ethansulphonic acid