Analysis of exercise-induced Na+-K+ exchange in rat skeletal muscle in vivo.
We aimed to quantify the Na(+)-K(+) exchange occurring during exercise in rat skeletal muscle in vivo. Intracellular Na(+) and K(+) content, Na(+) permeability ((22)Na(+) influx), Na(+)-K(+) pump activity (ouabain-sensitive (86)Rb(+) uptake) and Na(+)-K(+) pump alpha(2) subunit content ([(3)H]ouabain binding) were measured. Six-week-old rats rested (control animals) or performed intermittent running for 10-60 min and were then killed or were killed at 15 or 90 min following 60 min exercise. In the soleus muscle, intracellular Na(+) was 80% higher than in control rats after 60 min exercise, was still elevated (38%) after 15 min rest and returned to control levels after 90 min rest. Intracellular K(+) showed corresponding decreases after 15-60 min exercise, returning to control levels 90 min postexercise. Exercise induced little change in Na(+) and K(+) in the extensor digitorum longus muscle (EDL). In soleus, the exercise-induced rise in Na(+) and reduction in K(+) were augmented by pretreatment with ouabain or by reducing the content of muscular Na(+)-K(+) pumps by prior K(+) depletion of the animals. Fifteen minutes after 60 min exercise, ouabain-sensitive (86)Rb(+) uptake in the soleus was increased by 30% but was unchanged in EDL, and there was no effect of exercise on [(3)H]ouabain binding measured in vitro or in vivo in either muscle. In conclusion, in the soleus, in vivo exercise induces a rise in intracellular Na(+), which reflects the excitation-induced increase in Na(+) influx and leads to augmented Na(+)-K(+) pump activity without apparent change in Na(+)-K(+) pump capacity.
Murphy
K T
KT
Institute of Phsiology and Biophysics, University of Aarhus, Arhus, Denmark. ktmurphy@unimelb.edu.au
Nielsen
O B
OB
Clausen
T
T
D000818:Animals; D001665:Binding Sites; D002034:Bumetanide / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology*; D010042:Ouabain / Q000378:metabolism / Q000494:pharmacology; D005082:Physical Exertion; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism; D012979:Sodium Radioisotopes; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013997:Time Factors
D004791:Enzyme Inhibitors; D012414:Rubidium Radioisotopes; D012979:Sodium Radioisotopes; D002034:Bumetanide; D010042:Ouabain; D012964:Sodium; C498532:Atp1a2 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium