Effect of endurance training on activators of glycolysis in muscle during exercise.
Endurance training attenuates exercise-induced increases in blood lactate at the same submaximal work rate. Three intramuscular compounds that influence muscle lactate production were measured in fasted non-trained (NT) and endurance-trained (T) rats. The T rats were subjected to a progressive endurance-training program. At the end of the program (11 wk), they were running 2 h/day at 31 m/min up a 15% grade 5 days/wk. NT and T rats were fasted for 24 h and then anesthetized (pentobarbital, iv) at rest or after running for 30 min at 21 m/min (15% grade). Blood lactate levels were significantly lower in the T rats than in the NT rats after 30 min of running (2.3 +/- 0.2 vs. 3.9 +/- 0.2 mM). The lower blood lactate concentration was accompanied by lower plasma epinephrine (2.8 +/- 0.4 vs. 6.0 +/- 0.8 nM), adenosine 3', 3',5'-cyclic monophosphate (0.36 +/- 0.02 vs. 0.50 +/- 0.03 pmol/mg), mg), glucose 1,6-diphosphate (26 +/- 2 vs. 40 +/- 5 pmol/mg), and fructose 2,6-diphosphate (3.2 +/- 0.2 vs. 4.3 +/- 0.3 pmol/mg) in white quadriceps muscle in T than in NT rats. Red quadriceps muscle glucose 1,6-diphosphate and adenosine 3',5'-cyclic monophosphate were also lower in T than in NT rats. These adaptations may be responsible in part for the lower exercise-induced blood lactate in fasted rats as a consequence of endurance training.
Duan
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Zoology Department, Brigham Young University, Provo, Utah 84602.
Winder
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D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D005635:Fructosediphosphates / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives*; D005958:Glucosephosphates / Q000378:metabolism; D006019:Glycolysis; D006728:Hormones / Q000097:blood; D007773:Lactates / Q000097:blood / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D010807:Physical Endurance; D005082:Physical Exertion; D051381:Rats; D017207:Rats, Sprague-Dawley
D005635:Fructosediphosphates; D005958:Glucosephosphates; D006728:Hormones; D007773:Lactates; D019344:Lactic Acid; D019298:Glucose-6-Phosphate; C027652:fructose 2,6-diphosphate; C016473:glucose-1,6-bisphosphate; D000242:Cyclic AMP