Study of the functional communication of α-and β-cells in pancreatic islets

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This study was designed for investigating that in living islets different kinds of cells, such as α-, β-and δ-cells respond in a similar manner to that in isolated cellular condition. Further, the communication between b-cell to b-cell in islets was also investigated. In the present study, we used whole islets of the rat and mouse instead of slices of pancreatic tissue for obtaining multicellular preparations, and applied the patch-clamp technique to single cells in the islet Identification of cells was carried out by obtaining electrical characteristics of the particular cell, according to Gopel et al. (J. Physiology, 1999; 2000).From our experiments, we obtained the following condusions:1) In β-cells reside in intact islets, repetitive burst patterns of action potential firings appear in response to the glucose stimulation, while such a oscillatory response is not observed in isolated β-cells.2) K^+-currents induced by Ca^<2+> play a role for the termination of the action potentials of β-cells.3) In islets, adjoining β-cells are electrically communicated with the gap junction whose conductance is about 1 nS.4) a-cells and δ-cells have different electrical properties, and the mechanisms of theses cells for responding glucose stimulation are also different5) β-cell in islets exhibit an exocytotic capacity much larger than isolated cells, and this effect is mediated at least in part by glucagon released from a-cells residing near the β-cells. Further, we found that the dynamics of intact β-cells is constructed with coupling of individual chaotic dynamics in single β-cells, and chaos can be an index of instability in pancreatic β-cells.