Effects of pH on membrane resistance in normal and dystrophic mouse skeletal muscle fibers

1983 ◽  
Vol 82 (1) ◽  
pp. 203-214 ◽  
Author(s):  
Lynne M. Kerr ◽  
Nick Sperelakis
1998 ◽  
Vol 274 (4) ◽  
pp. C940-C946 ◽  
Author(s):  
Christopher D. Balnave ◽  
David G. Allen

The myoplasmic free Ca2+concentration ([Ca2+]i) was measured in intact single fibers from mouse skeletal muscle with the fluorescent Ca2+ indicator indo 1. Some fibers were perfused in a solution in which the concentration of Na+ was reduced from 145.4 to 0.4 mM (low-Na+solution) in an attempt to activate reverse-mode Na+/Ca2+exchange (Ca2+ entry in exchange for Na+ leaving the cell). Under normal resting conditions, application of low-Na+ solution only increased [Ca2+]iby 5.8 ± 1.8 nM from a mean resting [Ca2+]iof 42 nM. In other fibers, [Ca2+]iwas elevated by stimulating sarcoplasmic reticulum (SR) Ca2+ release with caffeine (10 mM) and by inhibiting SR Ca2+ uptake with 2,5-di( tert-butyl)-1,4-benzohydroquinone (TBQ; 0.5 μM) in an attempt to activate forward-mode Na+/Ca2+exchange (Ca2+ removal from the cell in exchange for Na+ influx). These two agents caused a large increase in [Ca2+]i, which then declined to a plateau level approximately twice the baseline [Ca2+]iover 20 min. If the cell was allowed to recover between exposures to caffeine and TBQ in a solution in which Ca2+ had been removed, the increase in [Ca2+]iduring the second exposure was very low, suggesting that Ca2+ had left the cell during the initial exposure. Application of caffeine and TBQ to a preparation in low-Na+ solution produced a large, sustained increase in [Ca2+]iof ∼1 μM. However, when cells were exposed to caffeine and TBQ in a low-Na+ solution in which Ca2+ had been removed, a sustained increase in [Ca2+]iwas not observed, although [Ca2+]iremained higher and declined slower than in normal Na+ solution. This suggests that forward-mode Na+/Ca2+exchange contributed to the fall of [Ca2+]iin normal Na+ solution, but when extracellular Na+ was low, a prolonged elevation of [Ca2+]icould activate reverse-mode Na+/Ca2+exchange. The results provide evidence that skeletal muscle fibers possess a Na+/Ca2+exchange mechanism that becomes active in its forward mode when [Ca2+]iis increased to levels similar to that obtained during contraction.


Channels ◽  
2012 ◽  
Vol 6 (4) ◽  
pp. 246-254 ◽  
Author(s):  
Tiffany C. Ho ◽  
Natalie A. Horn ◽  
Tuan Huynh ◽  
Lucy Kelava ◽  
Jeffry B. Lansman

2014 ◽  
Vol 69 (7) ◽  
pp. 821-830 ◽  
Author(s):  
A. T. Ludlow ◽  
E. E. Spangenburg ◽  
E. R. Chin ◽  
W.-H. Cheng ◽  
S. M. Roth

2015 ◽  
Vol 6 ◽  
Author(s):  
Tihomir Georgiev ◽  
Mikhail Svirin ◽  
Enrique Jaimovich ◽  
Rainer H. A. Fink

1990 ◽  
Vol 183 (2) ◽  
pp. 274-275
Author(s):  
M. Mambrini ◽  
D. Tricarico ◽  
H. Jockusch ◽  
D. Conte Camerino ◽  
V. Tortorella

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