Correlation between magnesium and potassium contents in muscle: role of Na(+)-K+ pump.
In young rats fed a Mg(2+)-deficient diet for 3 wk, Mg2+ and K+ contents in soleus and extensor digitorum longus muscles were significantly reduced and closely correlated. In isolated soleus muscles, Mg2+ depletion induced an even more pronounced loss of K+, and Mg2+ and K+ contents were correlated over a wide range (r = 0.95, P < 0.001). Extracellular Mg2+ (0-1.2 mM) caused no change in total or ouabain-suppressible 86Rb influx. After long-term incubation in Ca(2+)-Mg(2+)-free buffer with EDTA and EGTA, cellular Mg2+ and K+ contents were reduced by 35 and 15%, respectively, without any reduction in ATP and total or ouabain-suppressible 86Rb influx. In Mg(2+)-depleted muscles 42K efflux was increased by up to 42%, and repletion with Mg2+ produced a graded decrease. We conclude that Mg2+ and K+ contents are closely correlated in muscles Mg2+ depleted in vivo or in vitro and that neither extracellular nor moderate intracellular Mg2+ depletion affects total or Na(+)-K+ pump-mediated K+ influx. The reduced K+ content may rather be related to increased K+ efflux from the muscles.
Dørup
I
I
Institute of Physiology, University of Aarhus, Denmark.
Clausen
T
T
D000818:Animals; D005260:Female; D008274:Magnesium / Q000378:metabolism* / Q000494:pharmacology; D008275:Magnesium Deficiency / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*
D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D011188:Potassium