Effects of exercise training and exhaustion on 45Ca uptake by rat skeletal muscle mitochondria and sarcoplasmic reticulum.

Mitochondrial and sarcoplasmic reticular 45Ca2+ uptake and Ca2+-ATPase activity were determined in skeletal muscle from exercise trained and non-trained rats at rest or following short-term exhaustive exercise. In trained rats exercised to exhaustion, mitochondrial 45Ca2+ uptake was significantly depressed when compared to non-trained rats at rest. Ca2+-ATPase activity of sarcoplasmic reticulum from trained rats exercised to exhaustion was significantly increased as compared to trained rats at rest. These data suggest that the disruptive influence of Ca2+ accumulation in mitochondria isolated following exhaustive exercise may be diminished as a result of training.