Incidence of air pollution in the pulmonary surfactant system of the pigeon (Columba livia).
BACKGROUND: The integrity of both pulmonary surfactant and surfactant producing cells, type II pneumocytes, is essential for normal pulmonary function. Almost all studies about air pollution effects on the pulmonary surfactant system have been performed by biochemical techniques, using atmospheric pollutants in a much higher concentration than that found in polluted city air. A comparative study of the number of lamellar bodies (LB) (pulmonary surfactant precursors) from type II pneumocytes of pigeon lungs belonging to a contaminated city habitat and a noncontaminated countryside one has been carried out. METHODS: Lungs of both pigeon groups were subjected to standard processing for light microscopy. A representative number of histological sections from each lung were stained by Gomori's methenamine-silver nitrate technique, which appears to be a good marker for pulmonary LB. Diverse areas of atrial and parabronchial epithelia from each section were photographed, and then quantification of the number of LB per type II pneumocyte section was performed. The data were statistically analyzed and compared on the basis of the levels of atmospheric pollutants. RESULTS: Gomori's methenamine-silver nitrate technique is a useful staining method to study pneumocyte LB. The average of LB per cell section in city birds was about 33% less than in countryside specimens. Moreover, a great amount of macrophages in the lungs from city pigeons has been shown to be present, whereas this cell type is absent or very scarce in the lungs from country birds. CONCLUSIONS: Solid particles and high rates of nitrogen oxides in the polluted air, as well as the oxygen metabolites produced by the macrophages, would represent the main factors for the marked decrease in the amount of LB from type II pneumocytes.