Investigations on isolated islets in vitro. IX. Influence of food deprivation and glucose refeeding in vitro on insulin secretion

Summary Starvation resulted in a progressive decrease of insulin secretion in response to 15 mM glucose, but it neither inhibited insulin release completely nor changed the shape of the glucose response curve. Long-term fasting caused the glucose threshold to rise to 30 mM glucose during an incubation time of 15 min, whereas fed animals were characterized by a sigmoidal insulin response and a threshold level of 5 mM glucose during short-term incubation, too. Prolongation of incubation time (60 or 120 min) or pretreatment of isletsin vitro with 20 mM glucose for 60 min caused progressive lowering of the glucose threshold, indicating that glucoseper se influenced the effective stimulating concentration. The effect of starvation is not specific for glucose, since hormone secretion in response to glibenclamide, nicotinic acid and theophylline was also reduced, whereas theophylline can partly counteract the diminished release. Although the content of insulin as well as glucagon in the islets was reduced by food deprivation it is assumed that the islet hormone content is not responsible for the rise of the glucose threshold caused by starvation.