| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Pulmonary Division, Department of Medicine, Case Western Reserve University and Metrohealth Medical Center, Cleveland, Ohio 44109
Recent work indicates that endotoxemia elicits severe reductions in skeletal muscle force-generating capacity. The subcellular alterations responsible for these decrements have not, however, been fully characterized. One possibility is that the contractile proteins per se are altered in endotoxemia and another is that the mechanism by which these proteins are activated is affected. The purpose of the present study was to assess the effects of endotoxin administration on the contractile proteins by examining the maximum calcium-activated force (Fmax) and calcium sensitivity of single Triton-skinned fibers of diaphragm, soleus, and extensor digitorum longus (EDL) muscles taken from control and endotoxin-treated (8 mg/kg) rats. Fibers were mounted on a force transducer and sequentially activated by serial immersion in solutions of increasing Ca2+ concentration (i.e., pCa 6.0 to pCa 5.0); force vs. pCa data were fit to the Hill equation. All fibers were typed at the conclusion of studies using gel electrophoresis. Fmax, the calcium concentration required for half-maximal activation (Ca50), and the Hill coefficient were compared as a function of muscle and fiber type for the control and endotoxin-treated animals. Control group Fmax was similar for diaphragm, soleus, and EDL fibers, i.e., 112.34 ± 2.64, 111.55 ± 3.66, and 104.05 ± 4.33 kPa, respectively. Endotoxin administration reduced the average Fmax for fibers from all three muscles to 80.25 ± 2.30, 72.47 ± 2.97, and 78.32 ± 2.43 kPa, respectively (P < 0.001 for comparison of each to control). All fiber types in diaphragm, soleus, and EDL muscles manifested similar endotoxin-related reductions in Fmax. The Ca50 and the Hill coefficient for all fiber types and all muscles were unaffected by endotoxin administration. We speculate that these alterations in the intrinsic properties of the contractile proteins represent a major mechanism by which endotoxemia reduces muscle force-generating capacity.
free radicals; diaphragm; respiratory muscles; skinned fibers
This article has been cited by other articles:
|
|
 |
|
  H. W. H. van Hees, H. F. M. van der Heijden, C. A. C. Ottenheijm, L. M. A. Heunks, C. J. C. Pigmans, F. W. A. Verheugt, R. M. H. J. Brouwer, and P. N. R. Dekhuijzen Diaphragm single-fiber weakness and loss of myosin in congestive heart failure rats Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H819 - H828. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. S. Supinski and L. A. Callahan Free radical-mediated skeletal muscle dysfunction in inflammatory conditions J Appl Physiol, May 1, 2007; 102(5): 2056 - 2063. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. E. Nethery, S. Ghosh, S. C. Erzurum, and J. A. Kern Inactivation of neuregulin-1 by nitration Am J Physiol Lung Cell Mol Physiol, January 1, 2007; 292(1): L287 - L293. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Schnermann Exercise Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2002; 283(1): R2 - R6. [Full Text] [PDF]
|
|
|
|
 |
|
 L. A. Callahan, D. Nethery, D. Stofan, A. DiMarco, and G. Supinski Free Radical-Induced Contractile Protein Dysfunction in Endotoxin-Induced Sepsis Am. J. Respir. Cell Mol. Biol., February 1, 2001; 24(2): 210 - 217. [Abstract] [Full Text]
|
|
|
|
|
|
L. A. Callahan, Z. W. She, and T. M. Nosek Superoxide, hydroxyl radical, and hydrogen peroxide effects on single-diaphragm fiber contractile apparatus J Appl Physiol, January 1, 2001; 90(1): 45 - 54. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
