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Carbohydrate availability affects ammonemia during exercise after beta 2-adrenergic blockade
D Matthys1, W Derave, P Calders
1Department of Pediatric Cardiology, Institute of Kinesiology and Sport Sciences, University of Ghent, Belgium. dirk.matthys@rug.ac.be
Medicine and Science in Sports and Exercise
|May 5, 2000
Summary
Beta-adrenergic blockade impairs carbohydrate availability, leading to higher blood ammonia levels during exercise. Glucose supplementation can reduce ammonia but does not improve exercise capacity.
Area of Science:
- Exercise Physiology
- Biochemistry
Background:
- Beta-adrenergic blockade is known to increase blood ammonia concentrations during physical exertion.
- The underlying mechanisms, particularly the role of carbohydrate availability, require further investigation.
Purpose of the Study:
- To investigate the role of decreased carbohydrate availability in the exercise-induced increase in blood ammonia concentration during beta-adrenergic blockade.
- To assess the impact of glucose supplementation on ammonia levels and exercise capacity under beta-blockade.
Main Methods:
- Wistar rats were administered a beta 2-adrenoceptor blocker (ICI 118,551) or placebo, with or without glucose, before treadmill exercise.
- Blood and muscle samples were analyzed for ammonia, glucose, lactate, FFA, glycerol, BCAA, and glycogen content.
Main Results:
- Beta 2-blockade significantly reduced exercise duration and increased blood ammonia levels.
- Exercise-induced glycogen breakdown was inhibited by beta 2-blockade.
- Glucose supplementation normalized glycogen breakdown and reduced ammonia levels but did not enhance exercise capacity.
Conclusions:
- Impaired carbohydrate availability is suggested to be the primary cause of elevated blood ammonia during exercise following beta-blockade.
- While glucose can mitigate ammonia increase, it does not fully restore exercise performance compromised by beta-blockade.