Abstract

BACKGROUND
It was recently shown that mitochondrial function in pancreatic beta-cells is essential in nutrient-stimulated insulin secretion. The inhibition of mitochondrial DNA (mtDNA) transcription by ethidium bromide (EtBr) has been reported to suppress glucose-induced insulin secretion in beta-cell lines. This study was undertaken to examine the effects of EtBr on insulin secretion in isolated normal rat pancreatic islets, and to see whether antioxidants could protect the beta-cell function against the EtBr-induced impairment. METHODS: Pancreatic islets of normal Sprague-Dawley rats were isolated by intraductal injection of collagenase followed by Ficoll-gradient centrifugation. Isolated islets were treated with 0.2 +/- 2.0 microgram/mL of EtBr for 2 to 6 days, and the glucose-stimulated insulin secretion measured. The effects of the antioxidant, vitamin E and alpha-lipoic acid, on the EtBr-induced inhibition of insulin secretion were also examined. RESULTS: EtBr inhibited the basal and glucose-stimulated insulin secretion in normal rat pancreatic islets in a dose- and time-dependent manner. Vitamin E and alpha-lipoic acid prevented the EtBr-induced inhibition of insulin secretion. CONCLUSION: Our results show that antioxidant can protect normal rat pancreatic islets from the EtBr-induced inhibition of insulin secretion. This suggests that oxidative stress is involved in the pathogenesis of the insulin secretory defect associated with mitochondrial dysfunction.

• Keywords: Insulin secretion;Ethidium bromide;Mitochondrial DNA;Antioxidant;Rat pancreatic islets