|
|
|
|
|
|
|
||
The Journal of General Physiology, Vol 70, 1-21, Copyright © 1977 by The Rockefeller University Press
ARTICLES |
GE Kirsch, RA Nichols and S Nakajima
Tetanic stimulation of skeletal muscle fibers elicits a train of spikes followed by a long-lasting depolarization called the late after- potential (LAP). We have conducted experiments to determine the origin of the LAP. Isolated single muscle fibers were treated with a high potassium solution (5 mM or 10 mM K) followed by a sudden reduction of potassium concentration to 2.5 mM. This procedure produced a slow repolarization (K repolarization), which reflects a diffusional outflow of potassium from inside the lumen of the transverse tubular system (T system). Tetanic stimulation was then applied to the same fiber and the LAP was recorded. The time courses of K repolarization and LAP decay were compared and found to be roughly the same. This approximate equality held under various conditions that changed the time courses of both events over a wide range. Both K repolarization and the LAP became slower as fiber radius increased. These results suggest that LAP decay and K repolarization represent the same process. Thus, we conclude that the LAP is caused by potassium accumulation in the T system. A consequence of this conclusion is that delayed rectification channels exist in the T system. A rough estimation suggests that the density of delayed rectification channels is less in the T system than in the surface membrane.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  T. L. Dutka, R. M. Murphy, D. G. Stephenson, and G. D. Lamb Chloride conductance in the transverse tubular system of rat skeletal muscle fibres: importance in excitation-contraction coupling and fatigue J. Physiol., February 1, 2008; 586(3): 875 - 887. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Pasek, J. Simurda, and G. Christe The functional role of cardiac T-tubules explored in a model of rat ventricular myocytes Phil Trans R Soc A, May 15, 2006; 364(1842): 1187 - 1206. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. CLAUSEN Na+-K+ Pump Regulation and Skeletal Muscle Contractility Physiol Rev, October 1, 2003; 83(4): 1269 - 1324. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. M. Balog and R. H. Fitts Effects of depolarization and low intracellular pH on charge movement currents of frog skeletal muscle fibers J Appl Physiol, January 1, 2001; 90(1): 228 - 234. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Shepherd and H. B. McDonough Ionic diffusion in transverse tubules of cardiac ventricular myocytes Am J Physiol Heart Circ Physiol, September 1, 1998; 275(3): H852 - H860. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N Barrett and E. Barrett Excitation-contraction coupling in skeletal muscle: blockade by high extracellular concentrations of calcium buffers Science, June 16, 1978; 200(4347): 1270 - 1272. [Abstract] [PDF]
|
|
|
|
