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Study of Sugar Binding to the Sucrose-specific ScrY Channel of Enteric Bacteria Using Current Noise Analysis
Authors:C Andersen  R Cseh  K Schülein  R Benz
Institution:(1) Lankenau Medical Research Center, 100 Lancaster Ave., Wynnewood, PA 19096, USA, US;(2) University of Texas Medical Branch, Galveston, TX, USA, US
Abstract:CACO-2 BBE was used to determine the response of a gastrointestinal epithelium to tumor necrosis factor-α (TNF). Incubation of CACO-2 BBE with TNF did not produce any effect on transepithelial resistance (TER) within the first 6 hr but resulted in a 40–50% reduction in TER and a 30% decrease in I sc (short circuit current) relative to time-matched control at 24 hr. The decrease in TER was sustained up to 1 week following treatment with TNF and was not associated with a significant increase in the transepithelial flux of 14C]-d-mannitol or the penetration of ruthenium red into the lateral intercellular space. Dilution potential and transepithelial 22Na+ flux studies demonstrated that TNF-treatment of CACO-2 BBE cell sheets increased the paracellular permeability of the epithelium to Na+ and Cl. The increased transepithelial permeability did not associate with an increase in the incidence of apoptosis. However, there was a TNF-dependent increase in 3H]-thymidine labeling that was not accompanied by a change in DNA content of the cell sheet. The increase in transepithelial permeability was concluded to be across the tight junction because: (i) 1 mm apical amiloride reduced the basolateral to apical flux of 22Na+, and (ii) dilution potential studies revealed a bidirectionally increased permeability to both Na+ and Cl. These data suggest that the increase in transepithelial permeability across TNF-treated CACO-2 BBE cell sheets arises from an alteration in the charge selectivity of the paracellular conductive pathway that is not accompanied by a change in its size selectivity. Received: 4 March 1997/Revised: 3 November 1997
Keywords:: Tumor necrosis factor —  Cytokine —  Intestine —  Epithelia —  Tight junction —  Paracellular
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