Expression of K+-Cl- cotransporters in the α-cells of rat endocrine pancreas

The expression of K+-Cl- cotransporters (KCC) was examined in pancreatic islet cells. mRNA for KCC1, KCC3a, KCC3b and KCC4 were identified by RT-PCR in islets isolated from rat pancreas. In immunocytochemical studies, an antibody specific for KCC1 and KCC4 revealed the expression of KCC protein in a-cells, but not pancreatic beta-cells nor delta-cells. A second antibody which does not discriminate among KCC isoforms identified KCC expression in both alpha-cell and beta-cells. Exposure of isolated a-cells to hypotonic solutions caused cell swelling was followed by a regulatory volume decrease (RVD). The RVD was blocked by 10 muM [dihydroindenyl-oxy] alkanoic acid (DIOA; a KCC inhibitor). DIOA was without effect on the RVD in beta-cells. NEM (0.2 mM), a KCC activator, caused a significant decrease of a-cell volume, which was completely inhibited by DIOA. By contrast, NEM had no effects on beta-cell volume. In conclusion, KCCs are expressed in pancreatic alpha-cells and beta-cells. However, they make a significant contribution to volume hoineostasis only in alpha-cells. (C) 2004 Elsevier B.V. All rights reserved.