ISSN:
1432-2013
Keywords:
Skeletal Muscle
;
Contractility
;
Magnesium
;
Calcium
;
Excitation-Contraction
;
Coupling
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The penetration of magnesium from high-Mg Ringer's solution into skeletal muscle, and accompanying effects on intrafibre electrolyte composition, muscle contractility and Ca-exchange have been studied in isolated preparations of whole sartorius ofRana temporaria. Muscle magnesium, corrected for extracellular space, rose rapidly and then more slowly, and at 60 min in 20 mM Mg-Ringer it was calculated that intrafibre unbound Mg was increased by at least two-fold over the level in companion muscles in normal Ringer. Contractile response to direct, supramaximal stimulation was reduced in Mg-loaded muscles while resting membrane potential (E m) remained unaffected. Contracture in response to high-K was diminished while caffeine contracture was not changed. Muscles loaded with Mg also showed significant loss of fibre K and gained Na. Mg-loading caused a significant decrease in exchangeability of muscle Ca. Three fractions of exchangeable Ca in muscle were detected, characterised by half-times of circa 1.5, 7 and 50 min, respectively. In muscles soaked in high-Mg Ringer the half-times for these fractions were not different to the controls, but the quantities exchanged in the two slower fractions were reduced.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00592640
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