Study of Sugar Binding to the Sucrose-specific ScrY Channel of Enteric Bacteria Using Current Noise Analysis |
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Authors: | C Andersen R Cseh K Schülein R Benz |
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Institution: | (1) Lankenau Medical Research Center, 100 Lancaster Ave., Wynnewood, PA 19096, USA, US;(2) University of Texas Medical Branch, Galveston, TX, USA, US |
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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 |
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Keywords: | : Tumor necrosis factor — Cytokine — Intestine — Epithelia — Tight junction — Paracellular |
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