K-Cl cotransporter expression in the human kidney

The K-Cl cotransporter protein KCC1 is a membrane transport protein that me diates the coupled, electroneutral transport of K and Cl across plasma memb ranes. The precise cell type(s) in the kidney that express the K-Cl cotrans porter have remained unknown. The aim of the present investigation was to d efine the distribution of KCC1 mRNA in the human kidney. We used in situ hy bridization with a nonradioactive digoxigenin-labeled riboprobe. We identif ied abundant KCC1 mRNA expression in the epithelial cells throughout the di stal and proximal renal tubular epithelium. The transporter was also expres sed in glomerular mesangial cells and endothelial cells of the renal vessel s. These findings suggest that the K-Cl cotransporter may have an important role in transepithelial K and Cl reabsorption.