The effects of epinephrine on islet hormone secretion in the dog

We investigated the direct effects of physiological levels of epinephrine on the basal and arginine-stimulated secretion of insulin, glucagon, and somatostatin from the in situ pancreas in halothane-anaesthetized dogs. An IV infusion of 20 ng/kg/min of epinephrine increased plasma epinephrine levels to 918 +/- 103 pg/ml (P less than 0.001), and increased the baseline pancreatic output of insulin (P less than 0.05), glucagon (P less than 0.05) and somatostatin (P less than 0.05). The acute insulin response (AIR) to 2.5 g of arginine during this infusion of epinephrine was significantly higher (P less than 0.05) than in controls as were the acute glucagon response (AGR) (P less than 0.05) and the acute somatostatin response (ASLIR) (P less than 0.05). Plasma glucose levels increased slightly and transiently during infusion of epinephrine from 99 +/- 2 mg/dl to a maximum of 110 +/- 3 mg/dl (P less than 0.05). An IV infusion of 80 ng/kg/min of epinephrine produced plasma epinephrine levels of 2,948 +/- 281 pg/ml, and increased the baseline pancreatic output of insulin (P less than 0.05) and glucagon (P less than 0.05). In contrast, baseline somatostatin output decreased transiently during this high dose infusion of epinephrine. The AIR and ASLIR to arginine were both significantly lower (P less than 0.05) than those during the infusion of epinephrine at the low dose. The AGR to arginine remained potentiated (P less than 0.05). Plasma glucose levels increased from 99 +/- 3 mg/dl to 119 +/- 4 mg/dl (P less than 0.01). We conclude that the effect of epinephrine on islet hormone secretion is dependent on the plasma level of epinephrine. At stress levels of 900-1000 pg/ml, both insulin and somatostatin secretion are stimulated; only at near pharmacologic, or extreme stress levels, does epinephrine produce net inhibition.