The effect of prolonged glucagon infusions on the urinary excretion of catecholamines and 4-hydroxy-3-methoxymandelic acid and on adrenal medullary tissue levels of catecholamines in patients with severe cardiac disease

Effects of glucagon on myoelectrical activity of the stomach of conscious and anesthetized dogs

Effects of glucagon on gastric electrical and mechanical activities recorded by means of a chronically implanted suction electrode and a force strain gauge transducer were examined in conscious and anesthetized dogs. Glucagon (1-10 micrograms/kg) induced inhibition of gastric electrical activity together with mechanical activity in conscious dogs. The plasma glucagon level following exogenous glucagon administration which induced the inhibitory effects on electrical and mechanical activities was over 5 ng/ml. alpha- and beta-adrenoceptor blocking agents did not significantly alter the inhibitory effect of glucagon. Changes in plasma concentrations of glucose, cAMP, insulin, gastrin and catecholamines after glucagon administration were not correlated with the inhibitory action of glucagon on the gastric electrical and mechanical activities. Glucagon at higher concentrations (10(-6) -5 x 10(-6) g/ml) did not produce appreciable changes in motility of the canine gastric strips in vitro. In an anesthetized condition, the inhibitory action of glucagon was completely abolished. Results indicate that exogenously applied glucagon possibly acts directly on the central nervous system, and thus resulted in the inhibition of the gastric electrical and mechanical activities.

Glucagon effects on the human small intestine

In healthy volunteers, the effects of intravenously administered glucagon on small intestinal function was investigated. Bolus doses resulting in plasma glucagon concentrations of greater than 800 pg/ml (5 min after injection) abolished jejunal contractions for 4.4 +/- 0.4 (SEM) min after a latency period of 49 +/- 4 sec. During continuous intravenous glucagon infusion, jejunal dilatation and increase in mean transit time (MTT) occurred at plasma levels greater than 720 pg/ml, while inhibition of water and electrolyte absorption was observed only with plasma glucagon concentrations of 1760 +/- 114 pg/ml. Under these conditions, the propulsion of fasting intestinal contents was slowed without change in flow rate. The observed effects cannot be attributed to the simultaneously occurring rise in plasma insulin and glucose concentrations. Short-term increases in circulating glucagon concentration inhibit intestinal tone, contractions, and propulsion with only a minor effect on water and electrolyte absorption limited to a narrow concentration range of plasma glucagon. Neither effect occurs at glucagon levels likely to occur under physiologic concentrations. The latency period preceding the abolition of jejunal contractions suggests that glucagon does not act directly on intestinal smooth muscle cells.