Abstract
The purpose of the present study was to assess the effects of exogenously increasing the circulating levels of glucagon on the metabolic responses to exercise in rats. A total of six groups of rats were infused (iv) either with glucagon (20 or 50 ng·kg−1·min−1) or saline (0.9% NaCl), either in the resting state or during a bout of running exercise (45 min, 26 m·min−1, 0% grade). Blood samples were taken at the end of the 45-min experiment. Animals infused with glucagon at 50 ng·kg−1·min−1 showed significantly (P<0.01) higher mean plasma glucagon concentrations than animals infused with saline or glucagon at 20 ng·kg−1·min−1. In addition, exercise resulted in significantly (P<0.05) higher mean plasma glucagon concentrations, compared to rest, in all groups. In spite of these differences in glucagon concentrations, there were no significant (P>0.05) effects of exercise and glucagon infusion on mean hepatic glycogen, plasma glucose, insulin, C-peptide, β-hydroxybutyrate, or catecholamine concentrations. Although exercise resulted in a significant (P<0.01) increase in plasma glycerol and free fatty acid concentrations and a significant (P<0.05) decrease in glycogen in the soleus muscle, these responses were not affected by the glucagon infusion. These results suggest that the liver is non-responsive to physiological hyperglucagonemia in a short-term (45 min) exercise situation.
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This work was supported by the Natural Sciences and Engineering Research council of Canada and Fonds pour la Formation des Chercheurs et l'Aide à la Recherche (Government of Québec).
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Bélanger, P., Fillion, Y., Couturier, K. et al. Effects of inducing physiological hyperglucagonemia on metabolic responses to exercise. Eur J Appl Physiol 89, 8–13 (2003). https://doi.org/10.1007/s00421-002-0766-2
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DOI: https://doi.org/10.1007/s00421-002-0766-2