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 alpha-adrenergic agonist, and isoproterenol, a beta-adrenergic agonist, were added to the perfused solution. 1.2 microM phenylephrine suppressed glucagon secretion at 2.8 mM glucose, and it also decreased insulin secretion at 11.1 mM glucose. 240 nM isoproterenol enhanced glucagon secretion not only at 2.8 mM glucose, but also at 11.1 mM glucose, as well as insulin secretion at 11.1 mM. In order to study the role of intra-islet noradrenalin, phentolamine, an alpha-adrenergic antagonist, and propranolol, a beta-adrenergic antagonist, were infused with the perfused solution. 10 and 100 microM phentolamine caused an increase in insulin secretion, and 25 microM propranolol decreased insulin secretion, while they did not cause any change in glucagon secretion. From these results, it can be concluded that alpha-stimulation suppresses not only insulin but also glucagon secretion, while beta-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 influence on the A cell.