| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
MUSCLE CELL BIOLOGY AND CELL MOTILITY
1School of Biomedical Sciences, Victoria University of Technology, Melbourne, Victoria 8001; and 2Department of Zoology, La Trobe University, Melbourne, Victoria 3086, Australia
Submitted 8 December 2003 ; accepted in final form 17 February 2004
Single fibers of rat diaphragm containing different naturally occurring combinations of myofibrillar protein isoforms were used to evaluate the contribution of troponin C (TnC) isoforms to fiber type-related differences with respect to sensitivity to Sr2+ of the contractile system. Mechanically skinned fibers were studied for their isometric force vs. Sr2+ concentration ([Sr2+]) relationships and then analyzed electrophoretically for myofibrillar protein isoform composition. Our data demonstrate that fiber-type differences in Sr2+ dependence of contractile activation processes are primarily determined by the TnC isoform composition, with the slow isoform conferring on average a sevenfold greater sensitivity to Sr2+ than the fast isoform. Moreover, the ratio of TnC isoforms determined functionally from the force-pSr (–log10 [Sr2+]) curves is tightly (r2 = 0.97) positively correlated with that estimated electrophoretically. Together, these results validate the use of Sr2+ activation characteristics to distinguish fibers containing different proportions of fast and slow TnC isoforms and to study the mechanisms by which divalent cations activate the contractile apparatus. We also found that the functionally and electrophoretically determined ratios of TnC isoforms present in a fiber display similar sigmoidal relationships with the ratio of myosin heavy chain (MHC) isoform types expressed. These relationships 1) offer further insight in the functional and molecular expression of TnC in relation to the molecular expression of MHC isoform types and 2) may provide the basis for predicting sensitivity to Sr2+, TnC, and MHC isoforms in pure and hybrid skeletal muscle fibers.
muscle contraction; skeletal muscle; myofibrillar proteins; single fiber; sensitivity to strontium; sensitivity to calcium
This article has been cited by other articles:
|
|
 |
|
  G. S. Posterino and S. L. Dunn Comparison of the effects of inorganic phosphate on caffeine-induced Ca2+ release in fast- and slow-twitch mammalian skeletal muscle Am J Physiol Cell Physiol, January 1, 2008; 294(1): C97 - C105. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A. K. Birkeland, F. Swift, N. Tovsrud, U. Enger, P. K. Lunde, E. Qvigstad, F. O. Levy, O. M. Sejersted, and I. Sjaastad Serotonin increases L-type Ca2+ current and SR Ca2+ content through 5-HT4 receptors in failing rat ventricular cardiomyocytes Am J Physiol Heart Circ Physiol, October 1, 2007; 293(4): H2367 - H2376. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. F. Patterson, G. M. M. Stephenson, and D. G. Stephenson Denervation produces different single fiber phenotypes in fast- and slow-twitch hindlimb muscles of the rat Am J Physiol Cell Physiol, September 1, 2006; 291(3): 518 - 528. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W. A. Macdonald and D. G. Stephenson Effect of ADP on slow-twitch muscle fibres of the rat: implications for muscle fatigue J. Physiol., May 15, 2006; 573(1): 187 - 198. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. O'Connell, R. Blazev, and G. M. M. Stephenson Electrophoretic and functional identification of two troponin C isoforms in toad skeletal muscle fibers Am J Physiol Cell Physiol, February 1, 2006; 290(2): C515 - C523. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
