Effect of adrenaline on glucose kinetics during exercise in adrenalectomised humans

1. The role of adrenaline in regulating hepatic glucose production and musc le glucose uptake during exercise nas examined in six adrenaline-deficient, bilaterally adrenalectomised humans. Six sex- and age-matched healthy indi viduals served as controls (CON). 2. Adrenalectomised subjects cycled for 45 min at 68 +/- 1% maximum pulmona ry O-2 uptake ((V) over dot(O2,max)) followed by 15 min at 84 +/- 2% (V) ov er dot(O2,max) without (-ADR) or with (+ADR) adrenaline infusion, which ele vated plasma adrenaline levels (45 min, 4.49 +/- 0.69 nmol l(-1); 60 min, 1 2.41 +/- 1.80 nmol l(-1); means +/- S.E.M.). Glucose kinetics were measured using [3-H-3]glucose. 3. Euglycaemia was maintained during exercise in CON and -ADR, whilst in +A DR plasma glucose was elevated. The exercise-induced increase in hepatic gl ucose production was similar in +ADR and -ADR; however, adrenaline infusion augmented the rise in hepatic glucose production early in exercise. Glucos e uptake increased during exercise in +ADR and -ADR, but was lower and meta bolic clearance rate was reduced in +ADR. 4. During exercise noradrenaline and glucagon concentrations increased, and insulin and cortisol concentrations decreased, but plasma levels were simi lar between trials. Adrenaline infusion suppressed growth hormone and eleva ted plasma free fatty acids, glycerol and lactate. Alanine and beta-hydroxy butyrate levels were similar between trials. 5. The results demonstrate that glucose homeostasis was maintained during e xercise in adrenalectomised subjects. Adrenaline does not appear to play a major role in matching hepatic glucose production to the increase in glucos e clearance. In contrast, adrenaline infusion results in a mismatch by simu ltaneously enhancing hepatic glucose production and inhibiting glucose clea rance.