Lateral cell membranes and shunt resistance in rabbit esophageal epithelium.
OBJECTIVE
The structures that contribute to shunt resistance (Rs) in esophageal epithelium are incompletely understood, with 35-40% of Rs known to be calcium-dependent, reflecting the role of e-cadherin. Two calcium-independent candidates for the remaining approximately 60% of Rs have been identified: the glycoprotein matrix (GPM) within stratum corneum of esophageal epithelium, and the lateral cell membranes (LCMs) from neighboring cells.


METHODS
To determine the contribution of GPM and LCMs to Rs, rabbit esophageal epithelium was mounted in Ussing chambers so that transepithelial resistance (R(T)), a marker of Rs, could be monitored during luminal exposure to either glycosidases for disruption of the GPM or to hypertonic urea for separation of the LCMs.


RESULTS
Glycosidases had no effect on R(T). In contrast, hypertonic urea reduced R(T), increased fluorescein flux and widened the intercellular spaces. That urea reduced R(T), and so Rs, by widening the intercellular spaces, and not by altering the e-cadherin-dependent apical junctional complex, was supported by the ability of: (a) calcium-free solution to reduce R(T) beyond that produced by urea, (b) hypertonic urea to reduce R(T) beyond that produced by calcium free solution, (c) hypertonic sucrose to collapse the intercellular spaces and raise R(T), and (d) empigen, a zwitterionic detergent, to non-osmotically widen the intercellular spaces and reduce R(T).


CONCLUSIONS
These data indicate that the LCMs from neighboring cells are a major contributor to shunt resistance in esophageal epithelium. As resistor, they are distinguishable from the apical junctional complex by their sensitivity to (luminal) hypertonicity and insensitivity to removal of calcium.
Tobey
Nelia A
NA
Department of Medicine, University of North Carolina, Chapel Hill, NC 27599-7310, USA. neliatobey@aol.com
Djukic
Zorka
Z
Brighton
Luisa E
LE
Gambling
Todd M
TM
Carson
John L
JL
Orlando
Roy C
RC
D000704:Analysis of Variance; D000818:Animals; D015820:Cadherins / Q000378:metabolism* / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000502:physiology; D004195:Disease Models, Animal; D017097:Electric Impedance; D004594:Electrophysiology; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D004935:Esophageal Diseases / Q000378:metabolism; D004947:Esophagus / Q000187:drug effects / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000494:pharmacology; D006596:Hexosaminidases / Q000494:pharmacology; D006982:Hypertonic Solutions / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials; D009439:Neuraminidase / Q000494:pharmacology; D011336:Probability; D011817:Rabbits; D011897:Random Allocation; D012016:Reference Values; D012680:Sensitivity and Specificity; D013395:Sucrose / Q000494:pharmacology
D015820:Cadherins; D006982:Hypertonic Solutions; D013395:Sucrose; D006026:Glycoside Hydrolases; D006596:Hexosaminidases; D009439:Neuraminidase; C060638:glycopeptide alpha-N-acetylgalactosaminidase