Effects of glucagon on liver metabolism in intact dogs

Chloralose-anaesthesized dogs, starved for 24 hours, were used to determine the effects of 10 microgram/kg glucagon, administered i.v. as a single bolus injection, on liver substrates in situ (glycogen, glucose-1-phosphate, glucose-6-phosphate, glucose, fructose-6-phosphate, fructose-1,6-diphosphate, triose phosphates, glycerol-3-phosphate, phosphoenolypyruvate, pyruvate, lactate, citrate, malate, ATP, ADP, and AMP). liver samples were obtained by instant deep-freezing with Wollenberger clamps on four consecutive occasions at 10-minute intervals. Heart rate and blood pressure were continuously monitored. Serial liver sampling per se had no significant effects on liver metabolism or systemic haemodynamics in a group of control animals. In a second group glucagon, administered after the initial freeze-clamp sampling to obtain baseline values, led to a marked activation of the glycogenolytic pathway resulting in glucose release from the liver.