Altered E-C coupling in triads isolated from malignant hyperthermia- susceptible porcine muscle

R. El-Hayek, M. Yano, B. Antoniu, J. R. Mickelson, C. F. Louis, N. Ikemoto

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Triad vesicles were isolated from normal (N) and homozygous malignant hyperthermia-susceptible (MHS) porcine skeletal muscle, and two types of sarcoplasmic reticulum Ca2+ release were investigated: 1) polylysine- induced Ca2+ release (direct stimulation of the junctional foot protein), and 2) depolarization-induced Ca2+ release (stimulation of the junctional foot protein via the dihydropyridine receptor). At submaximal concentrations of polylysine, the rates of induced Ca2+ release from the MHS triads were greater than from normal triads. The T tubules of polarized triads were depolarized by the K+-to-Na+ ionic replacement protocol. Higher grades of T-tubule depolarization resulted in higher rates of Ca2+ release from both MHS and normal triads but, when compared at a given grade of T-tubule depolarization, the release rate was always greater from the MHS than from normal triads. Thus the activity of the SR Ca2+ release channel is always higher in MHS than in normal muscle at a given submaximal dose of release trigger. This difference is observed when the channel is stimulated directly by polylysine or indirectly via a depolarization-induced activation of the T- tubule dihydropyridine receptor.

Original languageEnglish (US)
Pages (from-to)C1381-C1386
JournalAmerican Journal of Physiology - Cell Physiology
Issue number6 37-6
StatePublished - 1995


  • calcium release
  • junctional foot protein
  • sarcoplasmic reticulum
  • skeletal muscle


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