Interstitial K+ concentration in active muscle after myocardial infarction

doi:10.1152/ajpheart.00295.2006.—Previous work demonstrated that Na-K pump activity within skeletal muscle is attenuated in myo-cardial infarction (MI). This may lead to enhanced interstitial K concentration ([K]o) in the muscle. We tested the hypothesis that [K]o rises with muscle contraction and that, in rats with MI, the rate of rise in [K]o is greater than it is in control animals. Microdialysis probes were inserted in the skeletal muscle of six healthy control and six MI rats. The ends of the probes were then attached to the K electrodes, and [K]o was continuously measured. Muscle contraction was induced by electrical stimulation of the sciatic nerves for 1 min. Stimulation at 1 and 3 Hz increased muscle [K]o by 14.2 % and 44.7 % in controls and by 22.9 % and 62.8 % in MI rats (P 0.05 vs. controls), respectively. When ouabain, an inhibitor of Na-K pump, was added to the perfusate, muscle [K]o rose significantly. This effect of ouabain was significantly attenuated in MI animals. I