Effect of glucose infusion on muscle malonyl-CoA during exercise.
Previous work in this laboratory has shown that muscle malonyl-CoA, the inhibitor of carnitine palmitoyltransferase I (CPT I), decreased during exercise. Hepatic malonyl-CoA content decreases when glucose availability decreases such as during fasting or when the glucagon-to-insulin ratio increases such as during prolonged exercise or in response to insulin deficiency. To investigate the effect of glucose infusion on muscle malonyl-CoA during exercise, male rats were anesthetized (pentobarbital via venous catheters) at rest or after running (21 m/min, 15% grade) for 30 or 60 min. During exercise rats were infused with either glucose (0.625 g/ml) or saline at a rate of 1.5 ml/h. Gastrocnemius muscles and liver samples were frozen at liquid nitrogen temperature. Muscle malonyl-CoA decreased from 1.24 +/- 0.06 to 0.69 +/- 0.05 nmol/g with glucose infusion and to 0.43 +/- 0.04 nmol/g with saline infusion during 60 min of exercise. In the liver, glucose infusion prevented the drop in malonyl-CoA. This indicates that glucose infusion attenuates the progressive decline in muscle malonyl-CoA and prevents the decline in liver malonyl-CoA during prolonged exercise.
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Zoology Department, Brigham Young University, Provo, Utah 84602.
Winder
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D000818:Animals; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000008:administration & dosage* / Q000378:metabolism; D007262:Infusions, Intravenous; D008099:Liver / Q000378:metabolism; D008297:Male; D008316:Malonyl Coenzyme A / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D010084:Oxidation-Reduction; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
D005227:Fatty Acids; D008316:Malonyl Coenzyme A; D005947:Glucose