title: Regulation of glucose turnover at the onset of exercise in the dog.
abstract: The early responses of endogenous glucose production (Ra), glucose utilization (Rd), and glucoregulatory hormones to moderate treadmill exercise (12% incline, 100 m/min, 60 min) were examined in dogs. Rd increased rapidly and progressively from the start of exercise. The change in Ra, as estimated with a variable-volume model of glucose kinetics, was biphasic, with an abrupt increase by 8.5 +/- 2.3 mumol.min-1.kg-1, followed by a delayed further increase that matched Rd 11-22 min after the onset of exercise. The plasma glucagon-to-insulin molar ratio fell slightly at the onset of exercise and then increased gradually. The glucagon-to-insulin ratio was correlated with Ra over the entire exercise period (r = 0.63, P less than 0.0001), but not during the early part of exercise, when Ra increased rapidly. The catecholamine- (epinephrine plus norepinephrine) to-insulin molar ratio was correlated with Ra during the early period (r = 0.52, P less than 0.01) and over the entire period of exercise (r = 0.66, P less than 0.0001). Our results confirm previous demonstrations that the glucagon-to-insulin molar ratio is an important regulator of Ra during exercise. We hypothesize that the catecholamine-to-insulin molar ratio is important during the early period of exercise and possibly during late exercise as an additional regulatory factor to the glucagon-to-insulin molar ratio.
authors.affiliation: Department of Physiology, University of Toronto, Ontario, Canada.
authors.forename: P D
authors.initials: PD
authors.lastname: Miles
authors.forename: D T
authors.initials: DT
authors.lastname: Finegood
authors.forename: H L
authors.initials: HL
authors.lastname: Lickley
authors.forename: M
authors.initials: M
authors.lastname: Vranic
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004285:Dogs; D004837:Epinephrine / Q000097:blood; D005934:Glucagon / Q000097:blood; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000097:blood; D007700:Kinetics; D009638:Norepinephrine / Q000097:blood; D005082:Physical Exertion / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D005934:Glucagon; D005947:Glucose; D009638:Norepinephrine; D004837:Epinephrine