Calcium uptake in skeletal muscle mitochondria. II. The effects of long-term chronic and acute exercise.
In order to ascertain the effects of long-term exercise training and long-term exhaustive exercise on mitochondrial 45Ca2+ uptake and related variables in rat skeletal muscle, female rats were randomly divided into three groups: sedentary-rested (SR), trained-rested (TR), and trained-exhausted (TE). The trained groups were exercised five times per week on a treadmill for 22 weeks. At the conclusion of the training period, the TE group was exercised to exhaustion following their daily 1 h run. The 45Ca2+ uptake and endogenous mitochodrial Ca2+ content of skeletal muscle followed stepwise increases of approximately 25% and 50%, respectively, across the groups, suggesting that long-term exercise induces the mitochondria to play an important role as a Ca2+ uptake buffer. A 75--83% reduction in 45Ca2+ binding  in the TE group suggests a selective loss and partial saturation of membrane phospholipids with exhaustive exercise. The TE group had a two-fold greater content of mitochondrial Mg2+ than did the rested groups. It is speculated that the mitochondria accumulate Mg2+ during acute exercise to maintain the functional integrity of the membrane, thus offsetting the deleterious effects of excessive Ca2+ uptake
D000222:Adaptation, Physiological; D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D005221:Fatigue / Q000378:metabolism; D005260:Female; D007773:Lactates / Q000097:blood; D008274:Magnesium / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000378:metabolism*; D010806:Physical Education and Training; D005082:Physical Exertion; D051381:Rats; D013997:Time Factors
D002132:Calcium Radioisotopes; D007773:Lactates; D008274:Magnesium; D002118:Calcium