Adrenergic blockade prevents endotoxin-induced increases in glucose metabolism

Combined α- and β-adrenergic blockade was used to investigate the role of catecholamines in endotoxin-induced elevations in glucose kinetics. Glucose kinetics were measured before and for 4 h after the injection of endotoxin [100 μg/100 g body wt iv, 30% lethal dose (LD₃₀) at 24 h]. Adrenergic blockade was achieved by the bolus injection of phentolamine and propranolol followed by their continuous infusion. Endotoxin-treated rats exhibited a transient hyperglycemia and sustained (>4 h) increase in plasma lactate concentration, as well as elevated rates of glucose appearance (R(a), 83%), disappearance (R(d), 58%), recycling (160%), and metabolic clearance (23%). Adrenergic blockade prevented endotoxin-induced increases in plasma glucose concentration, R(a), R(d), and recycling but not glucose clearance. The increase in plasma lactate concentration was blunted by 35%. After 2 h, endotoxic animals infused with adrenergic antagonists developed hypoglycemia, which may have resulted from an increased plasma insulin concentration. The attenuation of elevated glucose turnover by adrenergic blockade in the endotoxin-treated animals was not due to a reduction in plasma glucagon level or differences in plasma insulin concentration. Administration of the α- or β-adrenergic antagonists separately blunted but did not prevent endotoxin-induced changes in glucose kinetics, and therefore the efficacy of the adrenergic blockade could not be assigned to a single receptor class. These results indicate that catecholamines are important contributory factors to many of the early alterations in carbohydrate metabolism observed during endotoxemia.