Premium
Calcium waves induced by hypertonic solutions in intact frog skeletal muscle fibres
Author(s) -
Chawla Sangeeta,
Skepper Jeremy N.,
Hockaday Austin R.,
Huang Christopher L.H.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0351c.xd
Subject(s) - ryanodine receptor , biophysics , depolarization , calcium , chemistry , egta , tonicity , membrane potential , anatomy , medicine , biology , biochemistry , organic chemistry
1 Regenerative Ca 2+ 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 Ca 2+ 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‐Ca 2+ 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.