1. Dobutamine in 5% (w/v) d-glucose was infused at sequential doses of 2, 5 and 10 μg min−1 kg−1, 45 min at each dose, into eight healthy male subjects, and the effects were compared with those produced by infusion of the corresponding volumes of 5% (w/v) d-glucose alone.
2. The energy expenditure increased and was 33% higher than control (P<0.001) at 10 μg of dobutamine min−1 kg−1. The respiratory exchange ratio decreased from 0.85 (sem 0.02) before infusion to 0.80 (sem 0.01) at 10 μg of dobutamine min−1 kg−1, but did not alter during the placebo infusion (P> 0.001).
3. Plasma noradrenaline concentrations were lower during the dobutamine infusion compared with during the infusion of d-glucose alone (P < 0.025). Plasma dopamine concentrations remained below 0.1 nmol/l throughout both infusions.
4. Compared with during the placebo infusion, the blood glucose concentration decreased (P < 0.001), the plasma glycerol and free fatty acid concentrations increased by 150 and 225%, respectively (both P < 0.001), and the plasma potassium concentration decreased from 3.8 (sem 0.07) to 3.6 (sem 0.04) mmol/l (P<0.01) during dobutamine infusion. The plasma insulin concentration increased at 2 and 5 μg of dobutamine min−1 kg−1 (P<0.001) with no further rise at 10 μg of dobutamine min−1 kg−1.
5. Compared with during the placebo infusion, the systolic and diastolic blood pressures and the heart rate increased during dobutamine infusion (P<0.01). At 10 μg of dobutamine min−1 kg−1, the systolic blood pressure was around 160 mmHg (P < 0.001) and the heart rate was around 92 (sem 8) beats/min compared with 59 (sem 4) beats/min during the placebo infusion (P < 0.001).
6. Dobutamine has metabolic effects. It is markedly thermogenic and lipolytic. It depresses the respiratory exchange ratio and endogenous noradrenaline secretion, stimulates insulin secretion and depresses the blood glucose concentration.
