AJP - Lung Cellular and Molecular Physiology, Vol 265, Issue 5 448-L455, Copyright © 1993 by American Physiological Society

ARTICLES

Degradation of surfactant protein B by alveolar type II cells

S. R. Bates and A. B. Fisher
Institute for Environmental Medicine, University of Pennsylvania, School of Medicine, Philadelphia 19104.

Surfactant protein B (SP-B) metabolism was studied in primary cultures of alveolar type II cells. Iodinated SP-B reconstituted with surfactant was incorporated rapidly into lung pneumocytes and degraded to trichloroacetic acid (TCA)-soluble products after a lag period of 1 h. Cellular degradation of SP-B occurred whether or not phospholipid liposomes or surfactant was added to the phospholipid-poor SP-B. Uptake and degradation of SP-B at 37 degrees C showed a linear increase up to 3 micrograms SP-B/ml after which the slope of the curve became less steep with increasing concentrations of SP-B in the media. After 4 h of incubation with SP-B, 35% of the SP-B processed was recovered as degradation products. Ninety-six percent of the degradation products were in the media and only 4% were recovered in the cell. The bulk of the breakdown of SP-B occurred inside the type II cells since degradation did not occur at 4 degrees C, showed a 1-h lag period, was proportional to the SP-B protein internalized by the cells, was inhibited 47% by ammonium chloride, was unaffected by the addition of protease inhibitors to the medium, and cell-conditioned medium produced only limited SP-B degradation. Alveolar macrophages also degraded SP-B, whereas other cell types degraded SP-B to a lesser extent. Thus the specificity of the metabolism of SP-B may be through the capability of lung cells to degrade SP-B.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				D. Jain, C. Dodia, A. B. Fisher, and S. R. Bates Pathways for clearance of surfactant protein A from the lung Am J Physiol Lung Cell Mol Physiol, December 1, 2005; 289(6): L1011 - L1018. [Abstract] [Full Text] [PDF]

				K. Zen, K. Notarfrancesco, V. Oorschot, J. W. Slot, A. B. Fisher, and H. Shuman Generation and characterization of monoclonal antibodies to alveolar type II cell lamellar body membrane Am J Physiol Lung Cell Mol Physiol, July 1, 1998; 275(1): L172 - L183. [Abstract] [Full Text] [PDF]

				Z.-Y. Li, Y. Suzuki, M. Kurozumi, H.-Q. Shen, and C.-X. Duan Removal of a dimeric form of surfactant protein C from mouse lungs: its acceleration by reduction J Appl Physiol, February 1, 1998; 84(2): 471 - 478. [Abstract] [Full Text] [PDF]

				S. R. Bates, J. Xu, C. Dodia, and A. B. Fisher Macrophages primed by overnight culture demonstrate a marked stimulation of surfactant protein A degradation Am J Physiol Lung Cell Mol Physiol, October 1, 1997; 273(4): L831 - L839. [Abstract] [Full Text] [PDF]