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beta-adrenergic blockade augments glucose utilization in horses during graded exercise
R J Geor1, K W Hinchcliff, R A Sams
1Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210, USA. rgeor@ker.com
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 24, 2000
Summary
Beta-blockade in horses significantly increases glucose production and utilization during exercise. This suggests beta-adrenergic mechanisms normally limit glucose utilization in exercising horses.
Area of Science:
- Equine physiology
- Exercise metabolism
- Autonomic nervous system
Background:
- Beta-adrenergic mechanisms play a role in regulating glucose metabolism.
- Understanding these mechanisms is crucial for equine exercise physiology.
Purpose of the Study:
- To investigate the impact of beta-adrenergic blockade on glucose production and utilization in exercising horses.
- To determine the role of beta-adrenergic pathways in carbohydrate metabolism during exercise.
Main Methods:
- Six horses underwent exercise tests at low and high intensities with and without propranolol (a beta-blocker).
- Measurements included plasma glucose, insulin, glucagon, catecholamines, and glucose kinetics (Ra and Rd).
- Carbohydrate and fat oxidation rates were assessed.
Main Results:
- Propranolol administration increased plasma glucose levels during exercise.
- Beta-blockade augmented both glucose production (Ra) and utilization (Rd).
- Carbohydrate oxidation increased, while fat oxidation decreased under beta-blockade.
Conclusions:
- Beta-adrenergic mechanisms restrain glucose utilization during equine exercise.
- Beta-blockade enhances glucose production and utilization, leading to increased carbohydrate oxidation.
- This highlights the significant role of the sympathetic nervous system in metabolic regulation during exercise.