We have recently reported functional evidence for the expression of K⁺-Cl^– cotransporters in rat pancreatic α-cells (Davies et al. 2002). In the present study we have investigated the expression of the KCC1 isoform of K⁺-Cl^– cotransporter in pancreatic islets.

Sprague-Dawley rats were killed humanely by stunning and cervical dislocation. RT-PCR was performed on RNA isolated from the pancreas, using primers designed to amplify the rat KCC1 isofom. A product of the expected size (320 kb) was obtained, which when sequenced showed 100 % identity with the published sequence for rat KCC1. The location of KCC1 expression in the exocrine pancreas was examined by immunocytochemical methods, using an antibody raised against the N-terminus of mouse KCC1 (Roussa et al. 2002). Primary antibody binding to 5 µm cryosections of rat pancreas was detected using fluorescently labelled secondary antibodies.

KCC1 expression was confined to cells on the periphery of the islets of Langerhans. In co-localisation studies, KCC1 expression was observed in glucagon-staining cells, but not in cells staining for insulin or somatostatin. Immunocytochemistry performed in isolated islet cells identified KCC1 only in the smaller cells of the preparation (volume 0.43 ± 0.06 pl; mean ± S.E.M., n = 26), which are known to be α-cells (Majid et al. 2001).

In conclusion, we have shown that KCC1 mRNA and protein are present in rat pancreas. Furthermore, KCC1 appears only to be expressed in the α-cells of the endocrine pancreas.

S.L.D. is supported by the MRC and P.L. is supported by the BBSRC.