Regulation of Na(+)-K+ pump activity in contracting rat muscle

J Physiol. 1997 Sep 15;503 ( Pt 3)(Pt 3):571-81. doi: 10.1111/j.1469-7793.1997.571bg.x.

Abstract

1. In rat soleus muscle, high frequency electrical stimulation produced a rapid increase in intracellular Na+ (Na+i) content. This was considerably larger in muscles contracting without developing tension than in muscles contracting isometrically. During subsequent rest a net extrusion of Na+ took place at rates which, depending on the frequency and duration of stimulation, approached the maximum transport capacity of the Na(+)-K+ pumps present in the muscle. 2. In isometrically contracting muscles, the net extrusion of Na+ continued for up to 10 min after stimulation, reducing Na+i to values 30% below the resting level (P < 0.001). This undershoot in Na+i, seen in both soleus and extensor digitorum longus muscles, could be maintained for up to 30 min and was blocked by ouabain or cooling to 0 degree C. 3. The undershoot in Na+i could be elicited by direct stimulation as well as by tubocurarine-suppressible stimulation via the motor endplate. It could not be attributed to a decrease in Na+ influx, to effects of noradrenaline or calcitonin gene-related peptide released from nerve endings, to an increase in extracellular K+ or the formation of nitric oxide. 4. The results indicate that excitation rapidly activates the Na(+)-K+ pump, partly via a change in its transport characteristics and partly via an increase in intracellular Na+ concentration. This activation allows an approximately 20-fold increase in the rate of Na+ efflux to take place within 10 s. 5. The excitation-induced activation of the Na(+)-K+ pump may represent a feed-forward mechanism that protects the Na(+)-K+ gradients and the membrane potential in working muscle. Contrary to previous assumptions, the Na(+)-K+ pump seems to play a dynamic role in maintenance of excitability during contractile activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Albuterol / pharmacology
  • Animals
  • Calcitonin Gene-Related Peptide / pharmacology
  • Cold Temperature
  • Dantrolene / pharmacology
  • Electric Stimulation
  • Enzyme Inhibitors / pharmacology
  • Isometric Contraction / drug effects
  • Isometric Contraction / physiology*
  • Male
  • Muscle Fibers, Skeletal / chemistry
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Fibers, Skeletal / enzymology
  • Muscle Relaxants, Central / pharmacology
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / physiology*
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Nicotinic Antagonists / pharmacology
  • Propranolol / pharmacology
  • Rats
  • Rats, Wistar
  • Saxitoxin / pharmacology
  • Sodium / metabolism
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Sympatholytics / pharmacology
  • Sympathomimetics / pharmacology
  • Tubocurarine / pharmacology

Substances

  • Enzyme Inhibitors
  • Muscle Relaxants, Central
  • Nicotinic Antagonists
  • Sympatholytics
  • Sympathomimetics
  • Saxitoxin
  • Sodium
  • Propranolol
  • Sodium-Potassium-Exchanging ATPase
  • Dantrolene
  • Calcitonin Gene-Related Peptide
  • Albuterol
  • NG-Nitroarginine Methyl Ester
  • Tubocurarine