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

J Physiol. 2001 Oct 15;536(Pt 2):351-9. doi: 10.1111/j.1469-7793.2001.0351c.xd.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

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

Substances

  • Anesthetics, Local
  • Calcium Channel Blockers
  • Calcium Channels, L-Type
  • Hypertonic Solutions
  • Phosphodiesterase Inhibitors
  • Ryanodine Receptor Calcium Release Channel
  • Tetracaine
  • Ryanodine
  • Caffeine
  • Sucrose
  • Potassium Chloride
  • Nifedipine
  • Calcium