Differences in Metabolic Responses to β‐Adrenergic Stimulation after Propranolol or Metoprolol Administration

Abstract

Isoprenaline, or the .beta.2-agonist terbutaline, was infused in healthy male volunteers and the plasma levels of insulin, glucose and free fatty acids (FFA) were determined. Saline, propranolol or the selective .beta.1-receptor antagonist, metoprolol, was administered i.v. prior to the infusion of the .beta.-stimulants. The two .beta.-receptor blockers inhibited isoprenaline-induced increase in chronotropy to about the same extent, while the effects on systolic and diastolic blood pressure were in accordance with a selective .beta.1-blocking effect of metoprolol and a non-selective .beta.-blocking action of propranolol. Quantitative differences were found between metoprolol and propranolol on the metabolic parameters. The effects can best be described in terms of .beta.1- or .beta.2-receptors, where effects on plasma FFA and glycerol levels seem to be mainly .beta.1-mediated. An apparent .beta.2-mediated effect was found for insulin release and hepatic glucose output.