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Osmotic water permeability of Necturus gallbladder epithelium

An electrophysiological technique that is sensitive to small changes in cell water content and has good temporal resolution was used to determine the hydraulic permeability (Lp) of Necturus gallbladder epithelium. The epithelial cells were loaded with the impermeant cation tetramethylammonium (TMA+)...

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Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1989
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Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2216222/
https://www.ncbi.nlm.nih.gov/pubmed/2732678
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description An electrophysiological technique that is sensitive to small changes in cell water content and has good temporal resolution was used to determine the hydraulic permeability (Lp) of Necturus gallbladder epithelium. The epithelial cells were loaded with the impermeant cation tetramethylammonium (TMA+) by transient exposure to the pore-forming ionophore nystatin in the presence of bathing solution TMA+. Upon removal of the nystatin a small amount of TMA+ is trapped within the cell. Changes in cell water content result in changes in intracellular TMA+ activity which are measured with intracellular ion-sensitive microelectrodes. We describe a method that allows us to determine the time course for the increase or decrease in the concentration of osmotic solute at the membrane surface, which allows for continuous monitoring of the difference in osmolality across the apical membrane. We also describe a new method for the determination of transepithelial hydraulic permeability (Ltp). Apical and basolateral membrane Lp's were assessed from the initial rates of change in cell water volume in response to anisosmotic mucosal or serosal bathing solutions, respectively. The corresponding values for apical and basolateral membrane Lp's were 0.66 x 10(-3) and 0.38 x 10(-3) cm/s.osmol/kg, respectively. This method underestimates the true Lp values because the nominal osmotic differences (delta II) cannot be imposed instantaneously, and because it is not possible to measure the true initial rate of volume change. A model was developed that allows for the simultaneous determination of both apical and basal membrane Lp's from a unilateral exposure to an anisosmotic bathing solution (mucosal). The estimates of apical and basal Lp with this method were 1.16 x 10(-3) and 0.84 x 10(-3) cm/s.osmol/kg, respectively. The values of Lp for the apical and basal cell membranes are sufficiently large that only a small (less than 3 mosmol/kg) transepithelial difference in osmolality is required to drive the observed rate of spontaneous fluid absorption by the gallbladder. Furthermore, comparison of membrane and transepithelial Lp's suggests that a large fraction of the transepithelial water flow is across the cells rather than across the tight junctions.
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spelling pubmed-22162222008-04-23 Osmotic water permeability of Necturus gallbladder epithelium J Gen Physiol Articles An electrophysiological technique that is sensitive to small changes in cell water content and has good temporal resolution was used to determine the hydraulic permeability (Lp) of Necturus gallbladder epithelium. The epithelial cells were loaded with the impermeant cation tetramethylammonium (TMA+) by transient exposure to the pore-forming ionophore nystatin in the presence of bathing solution TMA+. Upon removal of the nystatin a small amount of TMA+ is trapped within the cell. Changes in cell water content result in changes in intracellular TMA+ activity which are measured with intracellular ion-sensitive microelectrodes. We describe a method that allows us to determine the time course for the increase or decrease in the concentration of osmotic solute at the membrane surface, which allows for continuous monitoring of the difference in osmolality across the apical membrane. We also describe a new method for the determination of transepithelial hydraulic permeability (Ltp). Apical and basolateral membrane Lp's were assessed from the initial rates of change in cell water volume in response to anisosmotic mucosal or serosal bathing solutions, respectively. The corresponding values for apical and basolateral membrane Lp's were 0.66 x 10(-3) and 0.38 x 10(-3) cm/s.osmol/kg, respectively. This method underestimates the true Lp values because the nominal osmotic differences (delta II) cannot be imposed instantaneously, and because it is not possible to measure the true initial rate of volume change. A model was developed that allows for the simultaneous determination of both apical and basal membrane Lp's from a unilateral exposure to an anisosmotic bathing solution (mucosal). The estimates of apical and basal Lp with this method were 1.16 x 10(-3) and 0.84 x 10(-3) cm/s.osmol/kg, respectively. The values of Lp for the apical and basal cell membranes are sufficiently large that only a small (less than 3 mosmol/kg) transepithelial difference in osmolality is required to drive the observed rate of spontaneous fluid absorption by the gallbladder. Furthermore, comparison of membrane and transepithelial Lp's suggests that a large fraction of the transepithelial water flow is across the cells rather than across the tight junctions. The Rockefeller University Press 1989-04-01 /pmc/articles/PMC2216222/ /pubmed/2732678 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Osmotic water permeability of Necturus gallbladder epithelium
title Osmotic water permeability of Necturus gallbladder epithelium
title_full Osmotic water permeability of Necturus gallbladder epithelium
title_fullStr Osmotic water permeability of Necturus gallbladder epithelium
title_full_unstemmed Osmotic water permeability of Necturus gallbladder epithelium
title_short Osmotic water permeability of Necturus gallbladder epithelium
title_sort osmotic water permeability of necturus gallbladder epithelium
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2216222/
https://www.ncbi.nlm.nih.gov/pubmed/2732678