Alveolar epithelial clearance of protein.
Folkesson, Hans G., Michael A. Matthay, Bj[diaeresis]orn R.
Westr[diaeresis]om, Kwang J. Kim, B[diaeresis]orje W. Karlsson,
Randolph H. Hastings.
Cardiovascular Research Institute, University of California San
Francisco, 505 Parnassus Ave., HSW 1346, San Francisco, CA 94143
-0130, USA, Department of Animal Physiology, University of Lund,
Helgonav[umlaut]agen B, S-223 62 LUND, Sweden, Departments of
Medicine, Physiology and Biophysics, and Biomedical Engineering, Will
Rogers Institute Pulmonary Research Center, University of Southern
California, Los Angeles, CA. 90033, USA, Anesthesiology Service 125,
VA Medical Center, Department of Anesthesiology, University of
California San Diego, 3350 La Jolla Village Drive, San Diego, CA.
92161, USA
APStracts 3:0060A, 1996.
Substantial progress has been made in understanding the rate, the
pathways, and the mechanisms regulating alveolar protein removal from
the uninjured lung. Whole animal studies and cellular studies have
demonstrated that the majority of alveolar epithelial protein
clearance occurs by passive, non-degradative, diffusional pathways.
Some evidence, though, has been recently presented that alveolar
epithelial cells express an albumin-binding receptor as well as a
polymeric immunoglobulin receptor which both might be important for
alveolar epithelial clearance of protein. However, the contribution
of these receptors requires further studies. Little is known about
alveolar clearance of protein during pathological conditions; further
studies are required to determine the roles of the different cell
types in the lung for removal of protein from the alveolar spaces of
the lung. Alveolar macrophages are likely to play an important role
in the degradation and removal of insoluble protein from the distal
air spaces after acute lung injury. In conclusion, the present data
suggest that most proteins and peptides deposited on the epithelial
surfaces in the distal air spaces are cleared as intact molecules
predominantly via paracellular routes. The contribution of pinocytic
processes appear to be of minor importance for translocation of bulk
quantities of proteins or peptides across the alveolar epithelium.
Received 20 October 1995; accepted in final form 15 December
1995.
APS Manuscript Number A1362-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96