Effects of metoprolol and propranolol on some metabolic responses to catecholamines in the anaesthetized dog

Abstract:The effects of metoprolol (0.5 mg/kg i.v.) and propranolol (0.2 mg/kg i.v.) on the plasma FFA response to i.v. infused adrenaline and noradrenaline and on the blood glucose and lactate responses to adrenaline were studied in anaesthetized dogs. Both β‐blockers markedly reduced the plasma FFA response to noradrenaline. Metoprolol differed from propranolol by inhibiting the plasma FFA response to adrenaline significantly less than that to noradrenaline. The lactacidemic effect of adrenaline was somewhat reduced by metoprolol and abolished by propranolol. The slight increase of blood glucose concentration produced by adrenaline was not significantly affected by either blocker. Adrenaline elicited a marked increase of the arterial blood pressure after propranolol treatment, whereas a slight hypotensive effect was observed after administration of metoprolol or in control experiments. It is suggested that the effects of metoprolol could be ascribed to inhibition of adrenergic β1‐receptor mediated actions, while those of propranolol were due to combined β1and β2‐receptor blockade.