A study of elucidating the effects of exercise on muscle Na-K pump in hypokalemia

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In this report, we investigated (1) effects of endurance training on lower skeletal muscle Na-K pump of hypokalemic and diabetic rats, (2) frequency response of evoked muscle potential relating to fatigue and hypokalemia.Rats of training and non-training groups were bred with deionized water and a KィイD1+ィエD1-deficient diet. The training group rats were trained with a treadmill running at 12 m/min for 30 minutes, 3 times a week.The distance rats could run, plasma KィイD1+ィエD1 content and lactate threshold of the trained rats after about 6 weeks' training were significantly greater than those of the untrained ones. Intracellular KィイD1+ィエD1 content ([K]ィイD2iィエD2 ) in the EDL and the SOL of the trained rats was also significantly greater than that of the untrained ones. The decrease of [K]ィイD2iィエD2 in lower skeletal muscle induced by stimulation of sciatic nerve was significantly greater in the untrained rats than in the trained ones.These results indicate that the endurance training based on aerobic exercise delays the progress of hypokalemia in rats fed the KィイD1+ィエD1 -deficient diet, and that the Na-K pump in muscle cells activated by training plays an important role in protecting against the decline in plasma KィイD1+ィエD1.The break-point frequencies of EDL and SOL were 85 Hz and 15 Hz in normal rats, respectively. They decreased to 15 Hz and 5 Hz in hypokalemic rats, respectively. These results suggest that the frequency response of evoked potential is an useful index for evaluation of morbid nerve-muscle.