HCO 3 - -dependent volume regulation in [alpha]-cells of the rat endocrine pancreas

Ion transport activity in pancreatic α-cells was assessed by studying cell volume regulation in response to anisotonic solutions. Cell volume was measured by a video imaging method, and cells were superfused with either 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid-buffered or HCO ^sub 3^ ^sup -^ -buffered solutions. α-Cells did not exhibit a regulatory volume increase (RVI) in response to cell shrinkage caused by hypertonic solutions. A RVI was observed, however, in cells that had first undergone a regulatory volume decrease (RVD), but only in HCO ^sub 3^ ^sup -^ -buffered solutions. RVI was also observed in response to a HCO ^sub 3^ ^sup -^ -buffered hypertonic solution in which the glucose concentration was increased from 4 to 20 mM. The post-RVD RVI and the glucose-induced RVI were both inhibited by 10μM 5-(N-methyl-N-isobutyl) amiloride or 100μM 2,2'-(1,2-ethenediyl) bis (5-isothio-cyanatobenzenesulfonic acid), but not by 10μM benzamil nor 10μM bumetanide. These data suggest that Na^sup +^-H^sup +^ exchangers and Cl^sup -^-HCO ^sub 3^ ^sup -^ exchangers contribute to volume regulation in α-cells.[PUBLICATION ABSTRACT]