Effect of isoproterenol on glucose turnover and insulin secretion in the normal dog

Infusion of epinephrine in the dog causes a sustained hyperglycemia without increasing plasma insulin, whereas infusion of isoproterenol causes a transient hyperglecemia and increased plasma insulin. To investigate the basis for these differences, rates of hepatic glucose production and overall glucose uptake were determined using a primer-constant infusion of 3-³H]glucose in normal dogs, and these were correlated with plasma insulin levels. Infusion of epinephrine (0.2 μg/kg/min) for 3 hr caused a prompt and persistent hyperglycemia. Concomitantly glucose production was increased but returned to normal by 90 min. Plasma insulin and glucose uptake did not increase. Isoproterenol infusion (0.2 μg/kg/min) for 3 hr caused a transient hyperglycemia. Glucose production and uptake were increased during the entire period. Plasma insulin was also elevated. The transient hyperglycemic response to isoproterenol, therefore, is not due to inadequate glucose production. Infusion of the beta-adrenergic blocker, propranolol, prevented the hyperglycemia and increased hepatic glucose production normally produced by isoproterenol.