Exercise performance and hemodynamics during dietary potassium depletion in dogs.

Dietary potassium depletion plus high sodium intake has been reported to elevate resting heart rate and cardiac output and to cause heart failure during exercise. We implanted aortic root electromagnetic flowmeters and aortic and pulmonary artery catheters in five splenectomized dogs condition-trained to run at 9 km/h on an 11% grade for 20 min. Postoperatively, the dogs ate a potassium-enriched diet until completion of control studies; then potassium was withdrawn. During 4 wk of depletion, skeletal muscle potassium fell from 380 +/- 22 to 311 +/- 8 meq/kg, and muscle sodium rose from 142 +/- 14 to 207 +/- 27 meq/kg (mean +/- SE). Cardiac output, aortic blood pressure, heart rate, acceleration of aortic blood flow at rest or during exercise, and the oxygen cost of exercise remained at control levels. Serum creatine phosphokinase at rest, an indicator of rhabdomyolysis, was never elevated. A 24% dietary depletion of muscle potassium in the dog did not change resting and exercise hemodynamics and exercise performance from control.