[Description of mitochondrial K+-transport system during intensive physical work]

The content of potassium ions in rat liver mitochondria after intensive physical work (continuous swimming) is increased approximately 2-fold, while the rate of K+ efflux from the mitochondria is significantly reduced. A considerable increase of the "calcium capacity" and a decrease of the respiration rate in state 4 were found. The experimental results indicate that during intensive physical work the mitochondrial membrane resistance to the damaging effects is enhanced. A possible mechanism of these changes is discussed.