Expression of the Na+-K+-2Cl- cotransporter in α and β cells isolated from the rat pancreas

The expression of the Na+-K+-2Cl- cotransporter (NKCC1) in α cells and β cells from the rat pancreas was examined. Isolated α cells and β cells in a mixed islet cell preparation were identified by volume using video-imaging methods, and by the expression of glucagon or insulin. The expression of mRNA for NKCC1 in pancreatic islets was demonstrated by RT-PCR. Immunocytochemical studies showed that the NKCC1 protein was expressed in rat β cells, but not α cells. The activity of Na+-K+-2Cl- cotransporter was also examined, by studying cell volume regulation in response to HEPES-buffered, hypertonic solutions. A regulatory volume increase was observed in the β cells but not the α cells. It is concluded that the NKCC1 is expressed in rat pancreatic β cells but not α cells. This is consistent with the hypothesis that Cl- is accumulated above the expected equilibrium distribution in β cells, but is below equilibrium in α cells.