Effect of magnesium depletion on 3H-ouabain binding site concentration in rat skeletal muscle

In young (4-week-old) rats, dietary Mg depletion for 1.5 weeks was followed by a significant decrease in 3H-ouabain binding site or Na,K-pump concentration of up to 21% and in total K content of up to 11% in various hind limb muscles. K depletion was associated with a decrease in 3H-ouabain binding site concentration of up to 64% and in total K content of up to 31%. Mg depletion was associated with a similar correlation between the decrease in 3H-ouabain binding site concentration and total K content, as was K depletion (r = 0.98, p less than 0.001). Taken together, the results indicate that the decrease in the concentration of 3H-ouabain binding sites following Mg depletion is not primarily caused by Mg deficiency per se, but is probably secondary to the associated K deficiency. The decrease in Na,K-pump concentration may be of importance for the retardation of K repletion as well as the increase in digitalis toxicity observed with Mg deficiency.