Protein movement across cultured guinea pig trachea: specificity
and effect of transcytosis inhibitors.
Deffebach, Mark E., Charlene J. Bryan, Cain M. Hoy.
Division of Pulmonary and Critical Care Medicine, Oregon Health
Sciences University and Portland VA Medical Center, Portland, OR
APStracts 3:0099L, 1996.
Airway surface liquid (ASL) is a complex fluid with solutes including
electrolytes, lipids, mucins, and proteins. The proximal airways are
absorptive for most solutes, including proteins. We investigated the
process of protein movement across confluent primary cultures of
guinea pig trachea grown on filters using fluorescent labeled BSA,
ovalbumin (OA), and 70KD dextran (Dex). We found marked asymmetry of
BSA and OA transepithelial flux, with apical-to-basolateral flux (JA
B) 10x greater than the opposite direction (JB A) for both proteins.
The apparent permeability for Dex was the same as that for proteins
in the B A direction and showed no asymmetry. Increasing
concentrations of unlabeled BSA, OA, or transferrin inhibited (JA B)
for both BSA and OA without effecting Dex movement. Cooling reduced
(JA B) for BSA without effecting (JB A). Monensin and nocodazole each
reduced (JA B) for BSA and OA without effecting (JB A). Monensin
eliminated all asymmetry for BSA movement. Brefeldin A did not effect
(JA B) for either protein, but did increase (JB A) for BSA. Treatment
with the protease inhibitors increased (JA B) for BSA. Western
immunoblotting demonstrated immunologically intact protein in the
downstream compartment. We conclude that there is transcytosis of
proteins across cultured trachea epithelium in the apical-to
-basolateral direction, which is monensin sensitive, involves
microtubules, is not dependent on proteolysis, and not protein
species specific. This process may be important for maintenance of
the ASL, and defects in this process may contribute to the abnormally
thickened airway secretion seen in airway diseases.
Received 21 August 1995; accepted in final form 4 June 1996.
APS Manuscript Number L255-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 June 96