Cellular uptake of albumin from the lungs of anesthetized
rabbits.
Hastings, Randolph H., Hans G. Folkesson, Vibeke Petersen, Ricardo
Ciriales, and Michael A. Matthay.
Department of Anesthesia, San Francisco General Hospital; the
Cardiovascular Research Institute and Departments of Medicine,
Anesthesia, and Stomatology, University of California, San Franciso;
Anesthesiology Service, San Diego Department of Veterans Affairs
Medical Center; Department of Anesthesiology, University of
California, San Diego
APStracts 2:0089L, 1995.
Resolution of alveolar edema depends on clearance of serum protein, as
well as liquid from the alveolar space. Protein clearance is slower
than liquid clearance and may take days to weeks. Our earlier studies
presented evidence for the importance of paracellular removal of
soluble protein from the air spaces. However, long term protein
clearance may also depend on uptake by alveolar epithelial cells or
macrophages. This study examined cellular uptake of soluble human
albumin and insoluble colloidal gold-albumin from the lungs of
anesthetized rabbits. Native albumin was endocytosed by both alveolar
type I and type II cells and appeared in vesicles and endosomes.
Neither cell type took up colloidal gold-albumin over periods as long
as eight hours. Alveolar macrophages took up native albumin and
colloidal gold-albumin to a greater extent and more rapidly than
alveolar epithelial cells. The tracer proteins were found in
vesicles, endosomes and phagolysosomes. Similarly, cultured alveolar
macrophages took up native albumin more rapidly than cultured type II
cells. Thus, macrophages may be important in clearing precipitated
protein from the air spaces and they may have a role in completing
the clearance of soluble protein. The potential for transepithelial
transport of soluble alveolar protein exists, but it appears to be a
low capacity pathway based on this work and our prior studies.
Received 7 February 1995; accepted in final form 9 May 1995.
APS Manuscript Number L40-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 26 May 1995.