Roles of sp-a, sp-b and sp-c in modulation of lipid uptake by
pulmonary epithelial cells in vitro.
Horowitz, Ann D., Bahar Moussavian, and Jeffrey A. Whitsett.
Division of Pulmonary Biology, Children's Hospital Research
Foundation, Children's Hospital Medical Center, Cincinnati, Ohio
45229 USA
APStracts 2:0146L, 1995.
The effects of the surfactant proteins SP-A, SP-B and SP-C on binding
and endocytosis of fluorescently labeled lipid vesicles were studied
in rat type II epithelial cells and in MLE-12 cells, a pulmonary
adenocarcinoma cell line with alveolar cell characteristics.
Incorporation of SP-C in lipid vesicles markedly stimulated binding
to the cell membrane at 4 C and endocytosis of lipids at 37 C. SP-C
enhanced lipid uptake in MLE-12 cells, type II cells and NIH 3T3
cells. SP-B stimulated lipid uptake in MLE-12 cells, but to a lesser
degree. SP-B decreased the amount of lipid uptake stimulated by SP-C.
SP-A did not increase endocytosis of lipids by MLE-12 cells or type
II cells, but aggregates of lipid were observed associated withthe
cell surface in the presence of SP-A. Maintenance of active
surfactant in the lung may be achieved through the selective uptake
and degradation of surfactant subfractions depleted in SP-A and SP-B.
Received 2 March 1995; accepted in final form 8 August 1995.
APS Manuscript Number L66-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.