Effect of beta-receptor blockade on splanchnic and muscle metabolism during prolonged exercise in men.
The importance of beta-receptor stimulation for the metabolism and circulation in the liver and exercising muscle was studied in six men during 3 h of leg exercise at 50% of maximum oxygen uptake. At 160 min of exercise, 0.15 mg propranolol/kg body wt was given intravenously. The results were compared with a previously studied control group examined in the same way but without beta-receptor blockade. The data show that beta-blockade during prolonged leg exercise, compared with exercising controls, results in 1) reduced splanchnic and leg blood flows (P < 0.005-0.01); 2) higher epinephrine and norepinephrine levels (P < 0.001); 3) unchanged respiratory exchange values, indicating unchanged carbohydrate oxidation; 4) a less marked drop in leg glucose uptake, suggesting reduced muscle glycogenolysis; 5) a higher splanchnic glucose output (P < 0.05) but lower splanchnic uptakes of lactate and glycerol after propranolol (P < 0.025-0.01), i.e., diminished uptake of gluconeogenic precursors, indicating accelerated hepatic glycogenolysis; and 6) unchanged glycerol levels with a lower splanchnic glycerol uptake, indicating reduced lipolysis. The data imply that, despite lower glycogen stores during prolonged exercise, liver glycogenolysis, as opposed to exercising muscle glycogenolysis, may be accelerated during beta-receptor blockade.
Ahlborg
G
G
Department of Clinical Physiology, Huddinge Hospital, Sweden.
Juhlin-Dannfelt
A
A
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005990:Glycerol / Q000097:blood; D006003:Glycogen / Q000097:blood / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007773:Lactates / Q000097:blood; D007866:Leg / Q000098:blood supply; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D008168:Lung / Q000378:metabolism / Q000502:physiology; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology*; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology; D012039:Regional Blood Flow / Q000187:drug effects
D000319:Adrenergic beta-Antagonists; D001786:Blood Glucose; D007773:Lactates; D006003:Glycogen; D011433:Propranolol; D005990:Glycerol