EFFECTS OF ENDURANCE TRAINING ON SARCOPLASMIC RETICULUM Ca2+-ATPase ACTIVITY AFTER PROLONGED EXERCISE

Abstract

562 The effects of endurance training on sarcoplasmic reticulum (SR) Ca2+-ATPase activity after a single bout of prolonged exercise were investigated in the soleus (SOL) and deep vastus lateralis (DVL) muscles of Wistar rats. Following 10 weeks of endurance training, some of both trained and untrained rats were run on a treadmill at 25 m/min on a 10% grade until fatigued. Endurance training evoked a 27% decrease in SR Ca2+-ATPase activity in SOL but not in the DVL. In both SOL and DVL of untrained rats, SR Ca2+-ATPase activities were lowered after acute exercise to exhaustion. On the other hand, in SOL but not DVL of trained rats, the catalytic activities of the ATPase were unaltered as a result of exhaustive exercise. These data demonstrate that, in slow-twitch muscle, endurance training leads to changes in SR Ca2+-ATPase activity and prevents the onset of SR dysfunction that is induced during exercise in untrained muscle. The precise mechanisms underlying muscular fatigue are not known but may not involve SR dysfunction at least in slow-twitch muscle subjected to endurance training.