This study was supported by the Danish Biomembrane Research Center and the Danish Medical Research Council (j.nr. 12-1336). Cross-sectional fibre area was kindly measured by Adrian P. Harrison, Department of Cellular Physiology, Babraham Institute, Cambridge, UK. The technical assistance of Marianne Stürup-Johansen, Ebba de Neergaard, Tove Lindahl Andersen and Bente Mortensen is gratefully acknowledged.
The significance of active Na+,K+ transport in the maintenance of contractility in rat skeletal muscle
Article first published online: 2 OCT 2003
Scandinavian Physiological Society
Acta Physiologica Scandinavica
Volume 157, Issue 2, pages 199–209, June 1996
How to Cite
NIELSEN, O. B. and CLAUSEN, T. (1996), The significance of active Na+,K+ transport in the maintenance of contractility in rat skeletal muscle. Acta Physiologica Scandinavica, 157: 199–209. doi: 10.1046/j.1365-201X.1996.d01-748.x
- Issue published online: 2 OCT 2003
- Article first published online: 2 OCT 2003
- Cited By
- intracellular sodium;
- muscle fatigue;
- Na+,K+ pump;
The effects of reduced Na+,K+ pump capacity on contractile endurance and excitation-induced changes in intracellular Na+ content were investigated in isolated rat soleus and extensor digitorum longus muscles. Pre-incubation with 10-5m ouabain increased the rate of force decline measured over the first 5–20 s of tetanic contraction from 0.32 to 0.94% s-1 and 1.4 to 4.6% s-1 in soleus and extensor digitorum longus muscles, respectively. Soleus muscles from K+-deficient rats exhibited 54% reduction in the concentration of Na+,K+ pumps and the force decline during 30 s of 60 Hz stimulation was increased from 0.53 to 1.15% s-1. A similar change was induced in control muscles when a comparable reduction in the concentration of functional Na+,K+ pumps was elicited by pre-incubation with ouabain (10-6-2×10-6m). In soleus, the force decline during 60 s of 60 Hz stimulation showed linear correlation to the increase in intracellular Na+ content. In extensor digitorum longus, force decline and increase in Na+ content during 60 Hz stimulation were both four times faster than in soleus as measured over 15 s of excitation. These results indicate that during maximal contractions the Na+,K+ pump capacity is one of the determinants for the contractile endurance in skeletal muscle. Furthermore, the maintenance of contractile force seems to be a function of the rate of Na+-influx and this relationship may account for the difference in endurance between slow-twitch and fast-twitch muscles.