Abstract des Autors

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; 2) higher epinephrine and norepinephrine levels; 3) unchanged respiratory exchange values, indicating unchanged carbohydrate oxidation; 4) a less marked drop in legg glucose uptake, suggesting reduced muscle glycogenolysis; 5) a higher splanchnic glucose output but lower splanchnic uptakes of lactate and glycerol after propranolol, i.e., diminished uptake of gluconeogenic precursors, indicating accelerated hepatic glycogenolysis; and 6) unchanged glycerol levels with a lower splanchnic glycerol uptake, indicating reduced liplysis. The data imply that, despite lower glycogen stores during prolonged exercise, liver glycogenolysis, as opposed to exercisingmuscle glycogenolysis, may be accelerated during beta-receptor blockade. Verf.-Referat