Effect of epinephrine on carbohydrate metabolism in exercising dogs.

Well-trained dogs with indwelling arterial and venous catheters ran on a treadmill (15%, 133 m/minute). A mixture of 3-3H: glucose and 14C-glucose (U) or 14C-lactate was infused at a constant rate. Hepatic glucose output (Ra), metabolic clearance rate of glucose (MCR), the percent participation of plasma glucose (G) in lactate production (%L comes from G), peripheral glycogenolysis (GLY) and lactate turnover (RaL) were calculated. Three types of experiments were conducted: (1) Type A, in which Epinephrine (E, 0.5 microgram/kg min) was infused mid-exercise for 75 min; (2) Type B, in which E was infused for three hours and exercise started mid-infusion for 75 min; and (3) Type C in which E and exercise began at the same time. In Type A, E increased G less (+15 mg/dL) than at rest (+50 mg/dL). Unlike at rest, during run E transiently decreased the Ra. The hyperglycemia was entirely due to a marked decrease of MCR. In Type B, E delayed the exercise-induced rise of Ra; and in Type C it delayed the rise of MCR. In all three types E reduced the %L comes from G from the usual 40% to 18% to 20%, and it potentiated the exercise-induced rise of GLY. In Type C, during the first hour, about five times as much lactate was produced (722 mg/kg) as in control runs (149 mg/kg). Beta-blockade abolished all the effects of E on glucose, lactate, MCR, GLY, %L comes from G and RaL. delta Ra and delta MCR rose faster, and they reached values that were approximately twice normal.(ABSTRACT TRUNCATED AT 250 WORDS)