Malignant hyperthermia (MH) is a potentially fatal pharmacogenetic syndrome caused by exposure to halogenated volatile anesthetics and/or depolarizing muscle relaxants. We have measured intracellular Ca2+ concentration ([Ca2+]i) using double-barreled, Ca2+-selective microelectrodes in myoballs prepared from skeletal muscle of MH-susceptible (MHS) and MH-nonsusceptible (MHN) swine. Resting [Ca2+]i was approximately twofold in MHS compared with MHN quiescent myoballs (232 ± 35 vs. 112 ± 11 nM). Treatment of myoballs with caffeine or 4-chloro-m-cresol (4-CmC) produced an elevation in [Ca2+]i in both groups; however, the concentration required to cause a rise in [Ca 2+]i elevation was four times lower in MHS than in MHN skeletal muscle cells. Incubation of MHS cells with the fast-complexing Ca 2+ buffer BAPTA reduced [Ca2+]i, raised the concentration of caffeine and 4-CmC required to cause an elevation of [Ca 2+]i, and reduced the amount of Ca2+ release associated with exposure to any given concentration of caffeine or 4-CmC to MHN levels. These results suggest that the differences in the response of MHS skeletal myoballs to caffeine and 4-CmC may be mediated at least in part by the chronic high resting [Ca2+]i levels in these cells.
- 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′- tetraacetic acid
- Calcium homeostasis
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology