Surfactant protein a is degraded by alveolar macrophages.
Bates, Sandra R., and Aron B. Fisher.
The Institute for Environmental Medicine, University of
Pennsylvania, School of Medicine, Philadelphia, PA 19104-6068
APStracts 3:0077L, 1996.
The metabolism of iodinated lung surfactant protein A (SP-A) by
alveolar macrophages in primary culture was examined to determine the
role these cells play in the degradation of this surfactant protein.
SP-A was isolated from lung lavage obtained from normal bovine,
alveolar proteinosis patients, and silica-treated rats. SP-A (0.5
ug/ml) was incubated for 3 h with rat alveolar macrophages obtained
by lung lavage. Cell-association and degradation of human and rat SP
-A was three times greater than for bovine SP-A. 50% of total
macrophage-associated SP-A was degraded during the 3 h period.
Degradation was time, temperature and concentration dependent
following a 1 h lag period. SP-A degradation was intracellular since
NH4Cl inhibited degradation more than 50% and macrophage-conditioned
medium was ineffective. Ten times more SP-A was degraded by
macrophages than by type II cells isolated following elastase
digestion of rat lungs. There was little degradation of SP-A by HeLa
cells. We conclude that alveolar macrophages take up and degrade SP-A
and, thus, could contribute to the catabolism of SP-A in the lung.
Received 17 July 1995; accepted in final form 16 April 1996.
APS Manuscript Number L222-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96