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. 1997 Feb 1;498(Pt 3):571–586. doi: 10.1113/jphysiol.1997.sp021884

Relationship between depolarization-induced force responses and Ca2+ content in skeletal muscle fibres of rat and toad.

V J Owen 1, G D Lamb 1, D G Stephenson 1, M W Fryer 1
PMCID: PMC1159176  PMID: 9051571

Abstract

1. The relationship between the total Ca2+ content of a muscle fibre and the magnitude of the force response to depolarization was examined in mechanically skinned fibres from the iliofibularis muscle of the toad and the extensor digitorum longus muscle of the rat. The response to depolarization in each skinned fibre was assessed either at the endogenous level of Ca2+ content or after depleting the fibre of Ca2+ to some degree. Ca2+ content was determined by a fibre lysing technique. 2. In both muscle types, the total Ca2+ content could be reduced from the endogenous level of approximately 1.3 mmol l-1 (expressed relative to intact fibre volume) to approximately 0.25 mmol l-1 by either depolarization or caffeine application in the presence of Ca2+ chelators, showing that the great majority of the Ca2+ was stored in the sarcoplasmic reticulum (SR). Chelation of Ca2+ in the transverse tubular (T-) system, either by exposure of fibres to EGTA before skinning or by permeabilizing the T-system with saponin after skinning, reduced the lower limit of Ca2+ content to < or = 0.12 mmol l-1, indicating that 10-20% of the total fibre Ca2+ resided in the T-system. 3. In toad fibres, both the peak and the area (i.e. time integral) of the force response to depolarization were reduced by any reduction in SR Ca2+ content, with both decreasing to zero in an approximately linear manner as the SR Ca2+ content was reduced to < 15% of the endogenous level. In rat fibres, the peak size of the force response was less affected by small decreases in SR content, but both the peak and area of the response decreased to zero with greater depletion. In partially depleted toad fibres, inhibition of SR Ca2+ uptake potentiated the force response to depolarization almost 2-fold. 4. The results show that in this skinned fibre preparation: (a) T-system depolarization and caffeine application can each virtually fully deplete the SR of Ca2+, irrespective of any putative inhibitory effect of SR depletion on channel activation; (b) all of the endogenous level of SR Ca2+ must be released in order to produce a maximal response to depolarization; and (c) a substantial part (approximately 40%) of the Ca2+ released by a depolarization is normally taken back into the SR before it can contribute to force production.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Ashley C. C., Mulligan I. P., Lea T. J. Ca2+ and activation mechanisms in skeletal muscle. Q Rev Biophys. 1991 Feb;24(1):1–73. doi: 10.1017/s0033583500003267. [DOI] [PubMed] [Google Scholar]
  2. Bakker A. J., Lamb G. D., Stephenson D. G. The effect of 2,5-di-(tert-butyl)-1,4-hydroquinone on force responses and the contractile apparatus in mechanically skinned muscle fibres of the rat and toad. J Muscle Res Cell Motil. 1996 Feb;17(1):55–67. doi: 10.1007/BF00140324. [DOI] [PubMed] [Google Scholar]
  3. Baylor S. M., Chandler W. K., Marshall M. W. Sarcoplasmic reticulum calcium release in frog skeletal muscle fibres estimated from Arsenazo III calcium transients. J Physiol. 1983 Nov;344:625–666. doi: 10.1113/jphysiol.1983.sp014959. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Donaldson S. K. Peeled mammalian skeletal muscle fibers. Possible stimulation of Ca2+ release via a transverse tubule-sarcoplasmic reticulum mechanism. J Gen Physiol. 1985 Oct;86(4):501–525. doi: 10.1085/jgp.86.4.501. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Donoso P., Hidalgo C. Sodium-calcium exchange in transverse tubules isolated from frog skeletal muscle. Biochim Biophys Acta. 1989 Jan 16;978(1):8–16. doi: 10.1016/0005-2736(89)90491-4. [DOI] [PubMed] [Google Scholar]
  6. Donoso P., Prieto H., Hidalgo C. Luminal calcium regulates calcium release in triads isolated from frog and rabbit skeletal muscle. Biophys J. 1995 Feb;68(2):507–515. doi: 10.1016/S0006-3495(95)80212-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Dulhunty A. F. Feet, bridges, and pillars in triad junctions of mammalian skeletal muscle: their possible relationship to calcium buffers in terminal cisternae and T-tubules and to excitation-contraction coupling. J Membr Biol. 1989 Jul;109(1):73–83. doi: 10.1007/BF01870792. [DOI] [PubMed] [Google Scholar]
  8. Dulhunty A. F., Gage P. W. Effects of extracellular calcium concentration and dihydropyridines on contraction in mammalian skeletal muscle. J Physiol. 1988 May;399:63–80. doi: 10.1113/jphysiol.1988.sp017068. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Dulhunty A. F., Gage P. W., Lamb G. D. Differential effects of thyroid hormone on T-tubules and terminal cisternae in rat muscles: an electrophysiological and morphometric analysis. J Muscle Res Cell Motil. 1986 Jun;7(3):225–236. doi: 10.1007/BF01753555. [DOI] [PubMed] [Google Scholar]
  10. Ebashi S., Endo M., Otsuki I. Control of muscle contraction. Q Rev Biophys. 1969 Nov;2(4):351–384. doi: 10.1017/s0033583500001190. [DOI] [PubMed] [Google Scholar]
  11. Endo M., Iino M. Specific perforation of muscle cell membranes with preserved SR functions by saponin treatment. J Muscle Res Cell Motil. 1980 Mar;1(1):89–100. doi: 10.1007/BF00711927. [DOI] [PubMed] [Google Scholar]
  12. Fryer M. W., Stephenson D. G. Total and sarcoplasmic reticulum calcium contents of skinned fibres from rat skeletal muscle. J Physiol. 1996 Jun 1;493(Pt 2):357–370. doi: 10.1113/jphysiol.1996.sp021388. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Fuchs F. The binding of calcium to detergent-extracted rabbit psoas muscle fibres during relaxation and force generation. J Muscle Res Cell Motil. 1985 Aug;6(4):477–486. doi: 10.1007/BF00712584. [DOI] [PubMed] [Google Scholar]
  14. Harrison S. M., Bers D. M. The effect of temperature and ionic strength on the apparent Ca-affinity of EGTA and the analogous Ca-chelators BAPTA and dibromo-BAPTA. Biochim Biophys Acta. 1987 Aug 13;925(2):133–143. doi: 10.1016/0304-4165(87)90102-4. [DOI] [PubMed] [Google Scholar]
  15. Klein M. G., Kovacs L., Simon B. J., Schneider M. F. Decline of myoplasmic Ca2+, recovery of calcium release and sarcoplasmic Ca2+ pump properties in frog skeletal muscle. J Physiol. 1991 Sep;441:639–671. doi: 10.1113/jphysiol.1991.sp018771. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Lamb G. D., Junankar P. R., Stephenson D. G. Raised intracellular [Ca2+] abolishes excitation-contraction coupling in skeletal muscle fibres of rat and toad. J Physiol. 1995 Dec 1;489(Pt 2):349–362. doi: 10.1113/jphysiol.1995.sp021056. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Lamb G. D., Stephenson D. G. Calcium release in skinned muscle fibres of the toad by transverse tubule depolarization or by direct stimulation. J Physiol. 1990 Apr;423:495–517. doi: 10.1113/jphysiol.1990.sp018036. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Lamb G. D., Stephenson D. G. Control of calcium release and the effect of ryanodine in skinned muscle fibres of the toad. J Physiol. 1990 Apr;423:519–542. doi: 10.1113/jphysiol.1990.sp018037. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Lamb G. D., Stephenson D. G. Effect of Mg2+ on the control of Ca2+ release in skeletal muscle fibres of the toad. J Physiol. 1991 Mar;434:507–528. doi: 10.1113/jphysiol.1991.sp018483. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Lamb G. D., Stephenson D. G. Effects of intracellular pH and [Mg2+] on excitation-contraction coupling in skeletal muscle fibres of the rat. J Physiol. 1994 Jul 15;478(Pt 2):331–339. doi: 10.1113/jphysiol.1994.sp020253. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Lüttgau H. C., Spiecker W. The effects of calcium deprivation upon mechanical and electrophysiological parameters in skeletal muscle fibres of the frog. J Physiol. 1979 Nov;296:411–429. doi: 10.1113/jphysiol.1979.sp013013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Melzer W., Herrmann-Frank A., Lüttgau H. C. The role of Ca2+ ions in excitation-contraction coupling of skeletal muscle fibres. Biochim Biophys Acta. 1995 May 8;1241(1):59–116. doi: 10.1016/0304-4157(94)00014-5. [DOI] [PubMed] [Google Scholar]
  23. Mobley B. A., Eisenberg B. R. Sizes of components in frog skeletal muscle measured by methods of stereology. J Gen Physiol. 1975 Jul;66(1):31–45. doi: 10.1085/jgp.66.1.31. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Owen V. J., Lamb G. D., Stephenson D. G. Effect of low [ATP] on depolarization-induced Ca2+ release in skeletal muscle fibres of the toad. J Physiol. 1996 Jun 1;493(Pt 2):309–315. doi: 10.1113/jphysiol.1996.sp021385. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Pape P. C., Jong D. S., Chandler W. K., Baylor S. M. Effect of fura-2 on action potential-stimulated calcium release in cut twitch fibers from frog muscle. J Gen Physiol. 1993 Aug;102(2):295–332. doi: 10.1085/jgp.102.2.295. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Pape P. C., Jong D. S., Chandler W. K. Calcium release and its voltage dependence in frog cut muscle fibers equilibrated with 20 mM EGTA. J Gen Physiol. 1995 Aug;106(2):259–336. doi: 10.1085/jgp.106.2.259. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Shirokova N., García J., Pizarro G., Ríos E. Ca2+ release from the sarcoplasmic reticulum compared in amphibian and mammalian skeletal muscle. J Gen Physiol. 1996 Jan;107(1):1–18. doi: 10.1085/jgp.107.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Shirokova N., Ríos E. Activation of Ca2+ release by caffeine and voltage in frog skeletal muscle. J Physiol. 1996 Jun 1;493(Pt 2):317–339. doi: 10.1113/jphysiol.1996.sp021386. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Sitsapesan R., Williams A. J. The gating of the sheep skeletal sarcoplasmic reticulum Ca(2+)-release channel is regulated by luminal Ca2+. J Membr Biol. 1995 Jul;146(2):133–144. doi: 10.1007/BF00238004. [DOI] [PubMed] [Google Scholar]
  30. Somlyo A. V., Gonzalez-Serratos H. G., Shuman H., McClellan G., Somlyo A. P. Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle: an electron-probe study. J Cell Biol. 1981 Sep;90(3):577–594. doi: 10.1083/jcb.90.3.577. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Stephenson D. G., Wendt I. R., Forrest Q. G. Non-uniform ion distributions and electrical potentials in sarcoplasmic regions of skeletal muscle fibres. Nature. 1981 Feb 19;289(5799):690–692. doi: 10.1038/289690a0. [DOI] [PubMed] [Google Scholar]
  32. Stephenson E. W. Properties of chloride-stimulated 45Ca flux in skinned muscle fibers. J Gen Physiol. 1978 Apr;71(4):411–430. doi: 10.1085/jgp.71.4.411. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Stephenson G. M., Stephenson D. G. Endogenous MLC2 phosphorylation and Ca(2+)-activated force in mechanically skinned skeletal muscle fibres of the rat. Pflugers Arch. 1993 Jun;424(1):30–38. doi: 10.1007/BF00375099. [DOI] [PubMed] [Google Scholar]
  34. Westerblad H., Allen D. G. The role of sarcoplasmic reticulum in relaxation of mouse muscle; effects of 2,5-di(tert-butyl)-1,4-benzohydroquinone. J Physiol. 1994 Jan 15;474(2):291–301. doi: 10.1113/jphysiol.1994.sp020022. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Yoshioka T., Somlyo A. P. Calcium and magnesium contents and volume of the terminal cisternae in caffeine-treated skeletal muscle. J Cell Biol. 1984 Aug;99(2):558–568. doi: 10.1083/jcb.99.2.558. [DOI] [PMC free article] [PubMed] [Google Scholar]

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