Myoplasmic Ca2+ concentration during exertional rhabdomyolysis.

Exertional rhabdomyolysis can destroy muscle but the pathophysiology is unknown. Using intracellular selective microelectrodes, we found that intracellular Ca2+ concentration ([Ca2+]i) was 1.27 (0.17) mumol/L (median and interquartile range) in skeletal-muscle biopsy specimens from patients with exertional rhabdomyolysis compared with 0.12 (0.01) mumol/L in controls. 3 days treatment with dantrolene, a drug that inhibits Ca2+ release from the sarcoplasmic reticulum, decreased [Ca2+]i to 0.22 (0.05) mumol/L and accelerated patients' recovery. This study demonstrated that exertional rhabdomyolysis is associated with elevated [Ca2+]i, and that dantrolene has a beneficial effect in this syndrome.