Synthetic Chloride Channel Increases Fluid and Cation Reabsorption in Micro-Perfused Renal Proximal Tubules

In an attempt to clarify the mechanism of fluid and ion movement driven by chloride (Cl) conductance, we studied the effect of expressing a Cl channel forming peptide in the luminal membrane of micro-perfused rabbit renal proximal tubules. An increase in Cl conductance, as indicated by a Cl-dependent increase in apical membrane voltage (Va), was confirmed after the peptide (NK_4-M2GlyR) was perfused. In the presence of the peptide, reabsorption of fluid (Jv) was dramatically increased, a part of which was inhibited by HgCl_2. Concomitantly reabsorption of Na (J_<Na>) and Ca (J_<Ca>) was significantly increased. We propose that introduction of the new Cl conductance in the luminal membrane leads to a coordinated efflux of water across the membrane and an increase in cation translocation via paracellular pathway, resulting in an increase in Jv. This novel method is useful to address the mechanism of fluid transport driven by the Cl gradient