Adrenergic Modulation of Insulin and Glucagon Secretion from the Isolated Perfused Rat Pancreas

In order to observe the effect of the adrenergic system on pancreatic glucagon secretion in the isolated perfused rat pancreas, phenylephrine, an αadrenergic agonist, and isoproterenol, a β-adrenergic agonist, were added to the perfused solution. 1.2μM phenylephrine suppressed glucagon secretion at 2.8mM glucose, and it also decreased insulin secretion at 11.1mM glucose. 240nM isoproterenol enhanced glucagon secretion not only at 2.8mM glucose, but also at 11.1mM glucose, as well as insulin secretion at 11.1mM. In order to study the role of intra-islet noradrenalin, phentolamine, an α-adrenergic antagonist, and propranolol, a β-adrenergic antagonist, were infused with the perfused solution. 10 and 100μM phentolamine caused an increase in insulin secretion, and 25μM propranolol decreased insulin secretion, while they did not cause any change in glucagon secretion. From these results, it can be concluded that α-stimulation suppresses not only insulin but also glucagon secretion, while β-stimulation stimulates glucagon secretion, as well as insulin secretion. Intra-islet catecholamine may have some effect on the B cell, whereas it seems to have no inffuence on the A cell.