Abstract
Human epithelial Intestine 407 cells respond to hypotonic stimulation with activation of the volume-sensitive outwardly rectifying (VSOR) chloride channels. In cell-attached patches, the VSOR single-channel currents exhibit outward rectification and voltage-dependent inactivation at large positive potentials. We attempted to estimate the dimensions of the VSOR channel pore using a nonelectrolyte partitioning method. Effects of nonelectrolytes with different molecular sizes on the cell-attached single-channel events were observed by applying from the extracellular side. Ethylene glycol (Rh=2.7 Å), triethylene glycol (Rh=2.7 Å) and polyethylene glycols of molecular weight 200-300 (PEG 200-300: Rh=4.5-5.3 Å) effectively suppressed the single-channel outward current, whereas larger molecules (PEG 400-4000 with Rh=6.2-19.1 Å) had little or no effect on the channel current amplitude. Since all the molecules tested effectively decreased electro-conductivity of the bulk solution, it appears that the observed differential effect between PEG 200-300 and PEG 400-4000 on the VSOR single-channel current was due to their limited partitioning into the channel lumen. From the cut-off radius of the PEG molecules, the VSOR channel pore is assessed to be 6.3 Å. [Jpn J Physiol 54 Suppl:S131 (2004)]
