Glucose transport and equilibrium across the alveolar-airway
barrier of the rat.
Saumon, Georges, Genevi[grave]eve Martet, and Paule Loiseau.
INSERM U82, Facult[acute]e Xavier Bichat, 75018 Paris, France
APStracts 2:0155L, 1995.
The glucose concentration in the epithelial lining fluid (ELF) results
from a balance between cellular uptake and paracellular leakage. The
present study examines whether the ELF glucose concentration can be
predicted from the kinetics of airspace glucose transport obtained in
fluid-filled lungs. Isolated rat lungs (n=16) were filled via the
trachea with instillate containing 0-10 mM glucose; the perfusate
glucose concentration was 10 mM. The rate of glucose removal from
airspaces depended on luminal glucose concentration and was saturable
(maximum uptake rate = 101+/-8.6 [mu]mol/h/g dry lung weight,
apparent Km = 1.5+/-0.43 mM, R =0.79). Glucose removal was inhibited
by phloridzin but not by phloretin or by inhibiting lung glycolysis
with iodoacetic acid. Airspace glucose remained low when the initial
instillate glucose concentration was zero. The steady state
concentration in fluid filled lungs was estimated 0.15+/-0.034 mM. It
agreed with that (<1/20 plasma) calculated using glucose transport
kinetics and epithelium paracellular permeability. The ELF glucose
concentration obtained by bronchoalveolar lavage was 0.39+/-0.012
plasma in vivo and 0.39+/-0.021 perfusate in air-filled isolated
lungs. The equilibrium ELF/perfusate distribution ratio of
-methylglucose was similar to that of glucose. Thus, there is a major
difference between the alveolar steady state glucose concentration in
fluid-filled lungs and the ELF glucose concentration in aerated lungs
despite similar mechanisms of airspace glucose removal. This suggests
that glucose kinetics or access to uptake sites differ in air- and
fluid-filled lungs.
Received 10 March 1995; accepted in final form 9 August 1995.
APS Manuscript Number L78-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 September 1995.