REGULATORY VOLUME INCREASE IN RAT PANCREATIC BETA-CELLS

This study investigated regulatory volume increase (RVI) in rat pancre atic beta-cells. Volume changes in isolated beta-cells were measured b y a video-imaging method. Cell shrinkage was induced by exposure to so lutions made hypertonic by the addition of 100 mM man mannitol. In HEP ES-buffered solutions, beta-cells exhibited an RVI which was almost co mpletely abolished by 10 mu M bumetanide. These data indicate that Na-2Cl(-)-K+ cotransporters make a major contribution to RVI in beta-cel ls. In HCO3--buffered solutions, however, an RVI was observed in the p resence of 10 mu M bumetanide. This bumetanide-insensitive component o f RVI was inhibited by 100 mu M amiloride or 100 mu M 4,4'-diisothiocy anatostilbene-2,2'-disulphonic acid (DIDS). These data suggest that, i n addition to the Na+-2Cl(-)-K+ cotransporter, functionally coupled Na +-H+ exchangers and Cl--HCO(3)(-)exchangers may also contribute to RVI in pancreatic beta-cells.