Attenuation of postexercise ketosis in fasted endurance-trained rats.
Endurance-trained animals and human subjects have been reported to exhibit a lesser degree of postexercise ketosis than nontrained controls. We have studied the mechanism of this adaptation. Trained (2 h/day, 6 wk) and nontrained rats were fasted overnight and then run at 16 m/min up a 15% grade for 90 min. Trained rats had lower blood 3-hydroxybutyrate during exercise and during a 90-min postexercise period than nontrained rats. Liver malonyl coenzyme A (CoA), carnitine, and glycogen were not significantly different in the two groups at any time during and after exercise. Therefore these factors cannot be responsible for the difference in ketonemia. Plasma free-fatty acids and hepatic adenosine 3',5'-cyclic monophosphate were elevated in nontrained rats with respect to trained rats. These two differences could conceivably be responsible for a different ketogenic rate. In addition, 3-ketoacid CoA transferase activity of gastrocnemius muscle was increased by training. The increase in ketone oxidizing enzymes of muscle may also be partially responsible for the training-induced attenuation of postexercise ketonemia in these fasted rats.
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D020155:3-Hydroxybutyric Acid; D000138:Acidosis / Q000503:physiopathology*; D000222:Adaptation, Physiological; D000818:Animals; D002331:Carnitine / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005934:Glucagon / Q000097:blood; D006003:Glycogen / Q000378:metabolism; D006885:Hydroxybutyrates / Q000097:blood; D007662:Ketosis / Q000097:blood / Q000503:physiopathology*; D008099:Liver / Q000378:metabolism; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D010805:Physical Conditioning, Animal; D010807:Physical Endurance; D051381:Rats; D011919:Rats, Inbred Strains
D005230:Fatty Acids, Nonesterified; D006885:Hydroxybutyrates; D006003:Glycogen; D005934:Glucagon; D000242:Cyclic AMP; D002331:Carnitine; D020155:3-Hydroxybutyric Acid