Localization of thermogenesis induced by single infusion of ephedrine in dog

The localization of the thermogenic effect of ephedrine (1 mg.kg-1 infused intravenously over 10 min.) was studied in 6 fasted dogs anaesthetized with etorfin-acepromazin-N2O. Three experiments were performed in each animal to determine the effect of ephedrine on a) splanchnic oxygen uptake, b) lower leg oxygen uptake and c) the work of the heart. In all experiments whole body oxygen uptake was monitored. Following ephedrine administration the following significant changes were seen as whole body oxygen uptake increased 16%, and splanchnic and lower leg oxygen uptakes increased respectively from 38.4 to 42.3 and from 7.3 to 12.1% of the whole body control oxygen uptake. The pressure-volume work of the heart more than doubled. Significant changes were also seen in mean arterial blood pressure, pulse rate, cardiac output, splanchnic blood flow, and haematocrit and haemoglobin concentration. Plasma glycerol and free fatty acid concentrations increased after ephedrine, and the effects were not elicited by circulating catecholamines.