High concentrations of glucose are considered to be toxic for the pancreatic β-cell. However, the mechanisms underlying β-cell dysfunction and resulting cell death are not fully characterized. In the present study we have demonstrated that incubation of pancreatic islets and β-cells from ob/ob mice and Wistar rats with glucose induced a process of apoptotic β- cell death, as shown by DNA laddering, TdT-mediated dUTP-biotin nick end- labeling (TUNEL) technique, and by using DNA-staining dye HOECHST 33342. The obtained results show that the percentage of apoptotic cells was dependent on glucose concentration, being minimal at 11 mM glucose. At a concentration of 100 μM, aurintricarboxylic acid, an inhibitor of endonuclease activity, almost completely inhibited apoptosis triggered by 17 mM glucose. We have also shown that long term incubation with 100 μM sulfonylurea, tolbutamide, triggered apoptosis in pancreatic β-cells. The process of β-cell death induced by high glucose concentration and tolbutamide were Ca2+-dependent, because introduction to the culture medium of 50 μM D-600 or 200 μM diazoxide, which blocked glucose- and tolbutamide-induced [Ca2+](i) increase, inhibited apoptosis. Thus, this study shows for the first time that high glucose concentrations and tolbutamide induce apoptosis in pancreatic β-cells, and that this process is Ca2+-dependent.
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