Effect of chronic potassium depletion on muscle bioenergetics in rats

To test the hypothesis of muscle bioenergetic impairment in potassium depletion, chronic potassium-depleted rats and pair-fed control rats were studied with phosphorus 31 nuclear magnetic resonance measurements of leg muscle intracellular pH, phosphocreatine, inorganic phosphate, and adenosine triphosphate at rest and during maximal nontetanic stimulation, 48 hours after a swimming test. The potassium-depleted rats exhibited a significant hypokalemia, a metabolic extracellular alkalosis, and an intracellular acidosis. Their physical endurance was markedly reduced, and they displayed higher plasma creatine kinase levels than the control group. However, the phosphocreatine/inorganic phosphate ratio, which is a measure of the energy reserve of the cell, was similar in both groups at rest and during electrical stimulation and subsequent recovery. Resting muscle glycogen and relative intracellular acidification during stimulation did not differ in the two groups, arguing against an impairment of anaerobic metabolism in potassium depletion. These results indicate that the energy availability of muscle cell is unchanged during potassium deficiency.