Effect of exogenous insulin on first-phase insulin secretion

AIM: To investigate the effect of exogenous insulin on first-phase insulin secretion of rat islets in vitro. METHODS: Male SD rat islets were isolated using digestion by ductal injection of collagenase Ⅴ and incubated with exogenous insulin (100 μU/mL) for 0, 60, 120 and 240 min (n=8)respectively. After incubation with insulin, the islets were stimulated by glucose (16.7 mmol/L).The secretion amount of insulin was measured at 0, 3, 5, 10 and 30 min, respectively. RESULTS: The first-phase glucose-stimulated insulin release existed in all groups(P0.05). But the peak of first-phase insulin release decreased as the incubation time of exogenous insulin went by(P0.01). CONCLUSION: The first-phase glucose-induced insulin secretion is impaired by exogenous insulin pretreatment.