Effects of Acute Cardioselective and non-selective beta-adrenergic Blockade on Plasma Ammonia Levels in Exercising Dogs

The aim of this study was to assess plasma ammonia levels during acute treadmill exercise in dogs after intravenous administration of a single dose of different cardioselective (atenolol) and non-selective (sotalol and propranolol) β-adrenergic blocking drugs. The experiments were performed on 6 male mongrel dogs (20-25 kg) trained to run on a motor driven treadmill. After administration of saline or atenolol, there was no significant increase in plasma ammonia during exercise; propranolol and sotalol however, both non-selective β-blockers, produced a significant increase in plasma ammonia. Plasma levels of alanine and glutamine were not altered during exercise compared with resting values, and were not modified by the administration of β-blockers. It is not clear whether the different effects on exercise induced hyperammonemia are due to different effects on muscle ammonia formation or on the ammonia clearance by the liver.