Analysis of the intracellular signal pathway in the pancreatic b-cells by direct observation of exocytosis

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The purpose of the present study is to clarify the involvement of major radical species on the insulin release from the pancreatic beta-cells. To this end, we applied NO,O_<2">, and alpha-tochopherol on the islet cells. These radicals induced degranulation of the beta-cells. We also observed chemiluminescene in the pancreatic tissue in vivo perfused with MCLA containing medium. Stimulation of the tissue with glucose significantly increased the MCLA-dependent chemiluminescence especially in the vicinity of the islet. Therefore, it was concluded that elevation in the glucose concentration results in radical production in the tissue and radicals induces degranulation in the beta-cells. alpha-tocopherol also induced degranulation in the same tissue. This effect of alpha-tocopherol was blocked by some types of bovine serum albumin. The present study clarified that radicals have not only adverse effects on the beta-cell but also physiologically important role in signal pathway leading to insulin release. It should be also emphasized that the beta-cells has a special sensitivity to radicals, and some radical scavengers act as radical species in the b-cells,