Calcium waves induced by hypertonic solutions in intact frog skeletal muscle fibres

S Chawla, J N Skepper, A R Hockaday, C L Huang

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1. Regenerative Ca2+ waves and oscillations indicative of calcium-induced calcium release (CICR) activity were induced in fully polarized, fluo-3-loaded, intact frog skeletal muscle fibres by exposure to hypertonic Ringer solutions. 2. The calcium waves persisted in fibres exposed to EGTA-containing solutions, during sustained depolarization of the membrane potential or following treatment with the dihydropyridine receptor (DHPR)-blocker nifedipine. 3. The waves were blocked by the ryanodine receptor (RyR)-specific agents ryanodine and tetracaine, and potentiated by caffeine. 4. In addition to these pharmacological properties, the amplitudes, frequency and velocity of such hypertonicity-induced waves closely resembled those of Ca2+ waves previously described in dyspedic skeletal myocytes expressing the cardiac RyR-2. 5. Quantitative transmission and freeze-fracture electronmicroscopy demonstrated a reversible cell shrinkage, transverse (T)-tubular luminal swelling and decreased T-sarcoplasmic reticular (SR) junctional gaps in fibres maintained in and then fixed using hypertonic solutions. 6. The findings are consistent with a hypothesis in which RyR-Ca2+ release channels can be partially liberated from their normal control by T-tubular DHPR-voltage sensors in hypertonic solutions, thereby permitting CICR to operate even in such fully polarized skeletal muscle fibres.
Original languageEnglish
Pages (from-to)351-9
Number of pages9
JournalJournal of Physiology
Issue numberPt 2
Publication statusPublished - 2001


  • Anesthetics, Local
  • Animals
  • Caffeine
  • Calcium
  • Calcium Channel Blockers
  • Calcium Channels, L-Type
  • Calcium Signaling
  • Cell Membrane
  • Electrophysiology
  • Hypertonic Solutions
  • Ion Channel Gating
  • Membrane Potentials
  • Microscopy, Electron
  • Muscle Fibers, Skeletal
  • Muscle, Skeletal
  • Nifedipine
  • Phosphodiesterase Inhibitors
  • Potassium Chloride
  • Rana temporaria
  • Ryanodine
  • Ryanodine Receptor Calcium Release Channel
  • Sarcoplasmic Reticulum
  • Sucrose
  • Tetracaine

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