Magnesium,Potassium,and Sodium in “Red” and “White” Muscle in the Rat

Abstract

Summary

The concentrations of Mg, K, and Na were measured in the soleus (“red muscle”) and superficial fibers of the medial head of the gastrocnemius (“white muscle”) in rats weighing 100–120 g and 250–300 g. The concentrations of Mg and K were significantly lower and the concentration of Na was significantly greater in the soleus than in the gastrocnemius.

Addendum. Recent data on the unequal distribution of calcium (μmole/g, dry wt) (atomic absorption spectrophotometry) between red and white muscle are as follows (mean ± SD): for eight younger rats, soleus = 4.24 ± 0.32 and gastrocnemius = 5.65 ± 0.42 (p < 0.001); for eight older rats, soleus = 2.92 ± 0.29 and gastrocnemius = 5.02 ± 0.27 (p < 0.001). With aging, the calcium concentration decreased in both red (p < 0.001) and white (p < 0.005) muscle.