Glutamate transport modulation of paracellular permeability across
llc-pk1-f+ monolayers.
Welbourne, T. C., D. Chevalier, and X. Mu.
Department of Physiology, LSUMC-Shreveport
APStracts 3:0136E, 1996.
The role of extracellular glutamate in modulating paracellular
permeability was assessed in proximal tubule-like LLC-PK1-F+ cells
and a rabbit kidney derived cell line, RK-13. The cells were grown to
confluent monolayers on porous supports in a modified DMEM containing
1.8mM L-glutamine and 50[mu]M L-glutamate. Changes in paracellular
permeability related to cellular glutamate uptake were inferred from
measured transepithelial electrical resistance and L-glucose
permeability. In LLC-PK1-F+ monolayers reducing glutamate uptake, by
blocking transport, or eliminating extracellular production, by
inhibiting gamma glutamyltransferase, [delta]-GT, resulted in
decreased electrical resistance and increased L-glucose permeability.
Supplementing [delta]-GT inhibited monolayers with 1mM L-glutamate
restored both cellular glutamate and electrical resistance. These
results are consistent with glutamate transport playing a major role
in maintaining paracellular permeability in the LLC-PK1-F+
monolayers. On the other hand, in RK-12 monolayers expressing less
than 10 percent of the LLC-PK1-F+'s [delta]-GT activity blocking
their low rate of glutamate transport resulted in a much smaller
increase in paracellular permeability. These results are consistent
with a role for [delta]-GT and glutamate transport acting as a
functional unit in the modulation of the paracellular permeability.
Received 19 March 1996; accepted in final form 3 July 1996.
APS Manuscript Number E139-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996