In Vivo Response to α1‐Adrenoreceptor Stimulation in Human White Adipose Tissue

Objective: Recent studies in rats suggest an important effect of α₁‐adrenoreceptor stimulation on glucose uptake in white adipocytes. It is not known if α₁‐adrenoreceptor stimulation elicits similar metabolic effects in humans. Research Methods and Procedures: Three microdialysis catheters in abdominal subcutaneous adipose tissue were perfused with 0.00, 0.01, 0.10, 1.00, and 10.00 μM isoproterenol, phenylephrine, or phenylephrine plus 100 μM propranolol. Dialysate concentrations of ethanol, glycerol, glucose, and lactate were measured for estimating blood flow (ethanol‐dilution technique), lipolysis, and glycolysis, respectively. Results: Phenylephrine, with or without propranolol, did not elicit a change in ethanol ratio. In contrast, the ethanol ratio decreased markedly with isoproterenol. Dialysate glucose concentration decreased with phenylephrine with and without propranolol and increased with isoproterenol. Phenylephrine caused a dose‐dependent increase in dialysate glycerol concentration, with a maximal effect similar to that of isoproterenol. The effect was attenuated with propranolol. Discussion: Our findings suggest that α₁‐adrenoreceptor stimulation by phenylephrine increases glucose uptake and metabolism in human abdominal adipose tissue. Furthermore, phenylephrine elicits a marked increase in lipolytic activity in white adipose tissue through β‐adrenoreceptor activation.