Expression of the Na+-K+-2Cl(-) cotransporter in alpha and beta cells isolated from the rat pancreas

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