Influence of infused beta-adrenergic agonists on porcine blood metabolites and catecholamines

Anesthetized pigs were infused sequentially with increased concentrations of beta-adrenergic agonists. At selected times during infusion, blood pressure, heart rate and plasma concentrations of free fatty acids (FFA), glycerol, glucose, lactate, norepinephrine, epinephrine and dopamine were measured. Azaperone, a drug used to calm the pigs before anesthesia, caused hypotension and bradycardia but did not affect plasma metabolites. Infusion of norepinephrine, epinephrine, isoproterenol or clenbuterol produced changes in plasma metabolites and plasma catecholamines. These changes during norepinephrine infusion were attributed to the infused agonist, whereas those during epinephrine infusion might have resulted to some extent from release of norepinephrine. Plasma isoproterenol was not quantified because it interfered with the assay of epinephrine and dopamine so that it was not possible to distinguish between infused isoproterenol and release of endogenous epinephrine and dopamine. Infusion of clenbuterol caused a small increase in plasma norepinephrine so that some of the increase in plasma FFA, glycerol and lactate during clenbuterol infusion may result from release of endogenous norepinephrine.