Secretion uncouples glucose inhibition of glucagon-producing cells resulting in a simultaneous stimulation of both glucagon and insulin release

The effect of secretin on glucagon and insulin release and its interaction with glucose has been studied in cultured mouse pancreatic islets by column perifusion. Glucose alone showed the well-known stimulation of insulin release and inhibition of glucagon release. Addition of 10 mM secretin increased glucagon secretion at 3 mM d-glucose by 300% while no change in insulin release could be seen at this low glucose concentration. At maximal stimulation of insulin release by 20 mM d-glucose addition of 10 nM secretin increased insulin release by 30%. Despite this insulin concentration and the high glucose concentration an increase in glucagon secretion of 1800% was found. These effects of secretin were dose-dependent at 10 mM d-glucose with 1 nM secretin being the lowest effective dose.