Swim training increases glucose output from liver perfused in situ with glucagon in fed and fasted rats.
The effect of endurance swim training (3 hours per day, 5 days/week, for 10 weeks) on hepatic glucose production (HGP) in liver perfused in situ for 60 minutes with glucagon and insulin was studied in Sprague-Dawley rats. The experiments were performed in fed rats and in rats fasted for 24 hours, but with lactate (8 mmol/L) added to the perfusion medium. Liver glycogen content was significantly lower in fasted than fed rats (fasted untrained and trained: 14 +/- 4 and 11 +/- 3 micromol glycosyl U/g of liver wet weight (WW); fed untrained and trained: 205 +/- 11 and 231 +/- 11 micromol glycosyl U/g of liver WW; not significantly different in trained and untrained rats). Glucagon increased HGP in the 4 experimental groups, but the increases were more rapid and pronounced in trained than in untrained rats in both fed and fasted states. HGP values (area under the curve [AUC] in micromol/g of liver WW) were significantly higher in trained fed (112.1 +/- 7.1 v 85.9 +/- 12.2 in untrained rats) than in trained fasted rats (50.8 +/- 4.4 v 34.7 +/- 3.6 in untrained rats). When compared with untrained rats, the total amount of glucose released by the liver in response to glucagon in trained rats was approximately 30% higher in the fed state and approximately 45% larger in the fasted state. These results indicate that endurance training increases the response of both glycogenolysis and gluconeogenesis to glucagon.
Département de kinésiologie, Université de Montréal, Canada.
Réjean
R
Drouin
Geneviève
G
Robert
Martin
M
Milot
Denis
D
Massicotte
François
F
Péronnet
Carole
C
Lavoie
D000410:Alanine Transaminase / Q000378:metabolism; D000818:Animals; D019540:Area Under Curve; D004435:Eating / Q000502:physiology*; D005215:Fasting / Q000502:physiology*; D005934:Glucagon / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism*; D024981:Glycogen Phosphorylase / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D008099:Liver / Q000378:metabolism* / Q000502:physiology; D008112:Liver Glycogen / Q000378:metabolism; D008297:Male; D010477:Perfusion; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013550:Swimming / Q000502:physiology*
D008112:Liver Glycogen; D019344:Lactic Acid; D005934:Glucagon; D024981:Glycogen Phosphorylase; D000410:Alanine Transaminase; D005947:Glucose