Degradation of pulmonary surfactant disaturated phosphatidylcholines by alveolar macrophages.
Miles-PR; Ma-JY; Bowman-L
J Appl Physiol 1988; 64(6):2474-2481
The degradation of pulmonary surfactant disaturated phosphatidylcholines (DSPC) by alveolar macrophages was studied in- vitro. Tritium (H3) labeled surfactant DSPC was obtained from male Sprague-Dawley-rats that had been injected with H3 labeled choline- chloride. The DSPC was incubated with alveolar macrophages obtained from untreated rats at 37 degrees-C for up to 6 hours. DSPC concentrations ranged up to 100 micrograms per milliliter (microg/ml). In some experiments sonicated macrophages were used. The extent of DSPC degradation was determined. The products of DSPC degradation were identified. Approximately 40 percent of the labeled DSPC was degraded over the 6 hour period. The breakdown occurred most rapidly during the first hour and was relatively linear over the next 5 hours. The specific activity of DSPC decreased by about 6 percent over the 6 hour period, indicating that DSPC itself was destroyed and not reincorporated during the incubation period. Surfactant DSPC degradation was linear for concentrations up to 100microg/ml. Sonicated macrophages degraded DSPC faster than intact macrophages. Only water soluble DSPC degradation products and unchanged DSPC were found after incubation. Additionally, H3 labeled pulmonary surfactant was incubated with alveolar macrophages at 37 and 2 degrees-C for up to 100 minutes and the extent of uptake of radiolabel was determined. Approximately 6 percent of the tritiated DSPC was taken up by the macrophages after 90 minutes at 37 degrees-C. At 2 degrees-C the amount of uptake was decreased by 80 percent. The authors conclude that alveolar macrophages are capable of degrading pulmonary surfactant DSPC in- vitro. The DSPC is probably internalized by the cells before being degraded.
NIOSH-Author; Lung-cells; Alveolar-cells; Phospholipids; Dose-response; Catabolism; Physiological-chemistry; In-vitro-studies; Decomposition-products
Journal of Applied Physiology