Effect of Adrenaline and Glucose on Release of Glucagon and Insulin in vitro

IT is well established that glucagon induces hyperglycaemia in animals and man through its action on liver glycogenolysis¹ and gluconeogenesis². Adrenaline has similar metabolic effects on the liver^1,2 and it is often thought that both hormones play a physiological role as glycogenolytic agents in blood glucose homeostasis. Several authors, however, have reported that when adrenaline was infused directly in the portal vein its effects on blood glucose and hepatic glycogenolysis were much less pronounced than when the hormone was administeied into the systemic circulation^3–5. Moreover, Sokal et al. demonstrated both in vitro and in vivo that, in contrast to glucagon, doses of adrenaline within the physiological range had only small and transient effects on liver glycogen and Phosphorylase activity^6,7. They thus concluded that glucagon is the only agent promoting glycogenolysis in the liver in physiological conditions and suggested that the effect of moderate doses of adrenaline might be indirect, possibly mediated through stimulation of glucagon secretion.