A study on the mechanism of islet cell apoptosis caused by high levels of glucose

Objective:To explore the mechanism of islet cell apoptosis caused by glucose at different concentrations.Methods:The islet cells of SD adult rats were prepared by collagenase digestion,purified by Fcoll400 and cultured in RPMI1640.Different concentrations of glucose or mannitol were added into the monolayer of islet cells.The medium insulin concentration was measured by RIA.The apoptosis rate was measured by the flow cytometry and the bax and bcl-2 expressions were detected by immunoblot.Results:①With glucose concentration raised from 11.1 mmol/L to 22.2 mmol/L,the insulin concentration began to raise and reached the peak,then it began to decline.②With glucose at 11.1 mmol/L and 22.2 mmol/L,the apoptosis rate was the highest,while at 5.5 mmol/L,there was no significant difference compared with the controls. For the groups of mannitol-infused,there was no differences of bax or bcl-2 expressions and no difference of the apoptosis rate comparing with the controls.③With glucose infused,the bcl-2 expressions in 11.1 mmol/L and 22.2 mmol/L groups were negative,bax expression was positive;the bax and bcl-2 expressions were negative in the group of 33.3 mmol/L;the bax and bcl-2 expressions in the 5.5 mmol/L group showed no difference compared with the controls.Conclusion:Higher levels of glucose at 11.1mmol/L and 22.2 mmol/L lead to the release of more insulin and the raise of apoptosis rate.But with glucose concentration at 33.3 mmol/L,the release of insulin decreased and the apoptosis rate declined.Hyperosmolality could not cause the apoptosis of the islet cell.