Forearm metabolism during infusion of adrenaline: comparison of the dominant and non‐dominant arm

Human skeletal muscle metabolism is often investigated by measurements of substrate fluxes across the forearm. To evaluate whether the two forearms give the same metabolic information, nine healthy subjects were studied in the fasted state and during infusion of adrenaline. Both arms were catheterized in a cubital vein in the retrograde direction. A femoral artery was catheterized for blood sampling, and a femoral vein for infusion of adrenaline. Forearm blood flow was measured by venous occlusion strain‐gauge plethysmography. Forearm subcutaneous adipose tissue blood flow was measured by the local133Xe washout method. Metabolic fluxes were calculated as the product of forearm blood flow and a‐v differences of metabolite concentrations. After baseline measurements, adrenaline was infused at a rate of 0·3 nmol kg−1 min−1. No difference in the metabolic information obtained in the fasting state could be demonstrated. During infusion of adrenaline, blood flow and lactate output increased significantly more in the non‐dominant arm (8·12 ± 1·24 versus 6·45 ± 1·19 ml 100 g−1 min−1) and (2·99 ± 0·60 versus 1·83 ± 0·43 μmol 100 g−1 min−1). Adrenaline induced a significant increase in oxygen uptake in the non‐dominant forearm (baseline period: 4·98 ± 0·72 μmol 100 g−1 min−1; adrenaline period: 6·63 ± 0·62 μmol 100 g−1 min−1) while there was no increase in the dominant forearm (baseline period: 5·69 ± 1·03 μmol 100 g−1 min−1; adrenaline period: 4·94 ± 0·84 μmol 100 g−1 min−1). It is concluded that the two forearms do not respond equally to adrenaline stimulation. Thus, when comparing results from different studies, it is necessary to know which arm was examined.