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Calcium transients in developing mouse skeletal muscle fibres
Author(s) -
Capote Joana,
Bolaños Pura,
Schuhmeier Ralph Peter,
Melzer Werner,
Caputo Carlo
Publication year - 2005
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 - 10.1113/jphysiol.2004.081034
Subject(s) - cyclopiazonic acid , ryanodine receptor , calcium , chemistry , transient (computer programming) , endoplasmic reticulum , biophysics , medicine , endocrinology , time constant , biology , biochemistry , organic chemistry , computer science , electrical engineering , engineering , operating system
Ca 2 + transients elicited by action potentials were measured using MagFluo‐4, at 20–22°C, in intact muscle fibres enzymatically dissociated from mice of different ages (7, 10, 15 and 42 days). The rise time of the transient (time from 10 to 90% of the peak) was 2.4 and 1.1 ms in fibres of 7‐ and 42‐day‐old mice, respectively. The decay of the transient was described by a double exponential function, with time constants of 1.8 and 16.4 ms in adult, and of 4.6 and 105 ms in 7‐day‐old animals. The fractional recovery of the transient peak amplitude after 10 ms, F 2(10) / F 1 , determined using twin pulses, was 0.53 for adult fibres and ranged between 0.03 and 0.60 in fibres of 7‐day‐old animals This large variance may indicate differences in the extent of inactivation of Ca 2 + release, possibly related to the difference in ryanodine receptor composition between young and old fibres. At the 7 and 10 day stages, fibres responded to Ca 2 + ‐free solutions with a larger decrease in the transient peak amplitude (25% versus 11% in adult fibres), possibly indicating a contribution of Ca 2 + influx to the Ca 2 + transient in younger animals. Cyclopiazonic acid (1 μ m ), an inhibitor of the sarcoplasmic reticulum (SR) Ca 2 + ‐ATPase, abolished the Ca 2 + transient decay in fibres of 7‐ and 10‐day‐old animals and significantly reduced its rate in older animals. Analysis of the transients with a Ca 2 + removal model showed that the results are consistent with a larger relative contribution of the SR Ca 2 + pump and a lower expression of myoplasmic Ca 2 + buffers in fibres of young versus old animals.