Effects of dietary magnesium on sodium-potassium pump action in the heart of rats.
Sprague-Dawley rats were fed a basal AIN-76 diet containing 80, 200, 350, 500 or 650 mg of magnesium per kilogram of diet for 6 wk. Ventricular slices, as well as microsomal fractions, were prepared from the hearts and were used to determine sodium-potassium pump activity. Sodium-potassium pump activity was assessed in the microsomal membranes by determining the ouabain-inhibitable Na+, K+-ATPase activity and [3H]ouabain binding, and in the ventricular slices, by determining ouabain-sensitive 86Rb uptake under K+-free conditions. The ATPase activity increased with increasing dietary magnesium, so that in the hearts of those animals that were fed 500 and 650 mg of magnesium/kg diet, it was significantly greater than the activity in the hearts of the animals fed 80 and 200 mg/kg diet. Similarly, 86Rb uptake by heart slices from rats fed 500 and 650 mg of magnesium/kg diet was significantly greater than the uptake by heart slices from animals fed 80 and 200 mg/kg diet. [3H]Ouabain binding did not change with increasing dietary magnesium. Thus, magnesium deficiency appears to have no effect on the number of sodium-potassium pump sites, but does decrease the activity of the pump. It is suggested that this leads to an increase in intracellular Na+, resulting in a change in the membrane potential, and may contribute to the arrhythmias associated with magnesium deficiency.
Fischer
P W
PW
Nutrition Research Division, Health and Welfare Canada, Ottawa, Ontario.
Giroux
A
A
D000818:Animals; D004032:Diet; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008722:Methods; D008861:Microsomes / Q000032:analysis; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis
D012414:Rubidium Radioisotopes; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D011188:Potassium