Referenced in: none

Automatically associated channels: Kir1.1

Title: Probing the water permeability of ROMK1 and amphotericin B channels using Xenopus oocytes.

Authors: R Z Sabirov, S Morishima, Y Okada

Journal, date & volume: Biochim. Biophys. Acta, 1998 Jan 5 , 1368, 19-26

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/9459580

Abstract
Water permeability of ion channels in the plasma membrane of Xenopus oocytes was studied by simultaneously measuring the membrane conductance under two-electrode voltage-clamp and the cell size by video-imaging technique. The basal level of osmotic water permeability of oocyte plasma membrane was 15.9+/-0.98 microm/s (SE, n = 5). Extracellular application of pore-forming antibiotic amphotericin B at 5 microM developed macroscopic conductance of 995+/-70 microS (n = 5) and increased the osmotic water permeability of cell membrane by 44.9+/-4.1 microm/s. Meanwhile, after expressing ROMK1 channels, originally cloned from kidney, virtually no increase in the water permeability was observed even at the conductance level as high as 1113+/-47 microS (n = 5). This result suggests that even though potassium channels, like any others, are considered to be water-filled pores, K+-selective ion-transporting pathway remains virtually water-impermeable in physiological conditions, such as in kidney epithelia where huge water transport takes place at both apical and basolateral sides.