title: Effects of inducing physiological hyperglucagonemia on metabolic responses to exercise.
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 x kg(-1) x min(-1)) or saline (0.9% NaCl), either in the resting state or during a bout of running exercise (45 min, 26 m x min(-1), 0% grade). Blood samples were taken at the end of the 45-min experiment. Animals infused with glucagon at 50 ng x kg(-1) x min(-1) showed significantly (P<0.01) higher mean plasma glucagon concentrations than animals infused with saline or glucagon at 20 ng x kg(-1) x 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, beta-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.
authors.affiliation: Département de kinésiologie, Université de Montréal, C.P. 6128 succ. Centre-ville, H3C 3J7 Montréal, Québec, Canada.
authors.forename: Patrice
authors.initials: P
authors.lastname: Bélanger
authors.forename: Yovan
authors.initials: Y
authors.lastname: Fillion
authors.forename: Karine
authors.initials: K
authors.lastname: Couturier
authors.forename: Marie-Soleil
authors.initials: MS
authors.lastname: Gauthier
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lavoie
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000097:blood / Q000378:metabolism; D000818:Animals; D000842:Ankle / Q000503:physiopathology; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D002096:C-Peptide / Q000032:analysis / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000097:blood / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000378:metabolism; D005934:Glucagon / Q000008:administration & dosage* / Q000097:blood*; D005990:Glycerol / Q000097:blood / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006943:Hyperglycemia / Q000097:blood* / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood / Q000378:metabolism; D008112:Liver Glycogen / Q000097:blood / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D009638:Norepinephrine / Q000097:blood / Q000378:metabolism; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008112:Liver Glycogen; D006003:Glycogen; D005934:Glucagon; D005990:Glycerol; D020155:3-Hydroxybutyric Acid; D009638:Norepinephrine; D004837:Epinephrine