Correlation of mineral dust-induced changes in the composition of a fraction enriched in lung surfactant with pulmonary histologic lesions in rats

In previous work the composition of surfactant isolated from cell-free bronchoalveolar lavage (CF-BAL) from the right lungs of monkeys instilled with 500 mg of either generic bituminous, anthracite, quartz, or titanium dioxide dust was compared with that of surfactant isolated from CF-BAL from control left lungs. Exposure to quartz, anthracite, or titanium dioxide induced a significant increase in the amount of protein recovered, which was evident throughout most of the time period (1 year) studied. Exposure to quartz also induced a significant decrease in the total amount of lipid-associated phosphorus. To determine whether dust-induced changes in surfactant composition paralleled changes in lung morphology, consecutive studies were carried out in rats. Rats were instilled with 50 mg of either quartz or anthracite dust/kilogram body weight. One milligram of bituminous dust was instilled with every 5 mg of quartz dust as a marker to indicate dust location. Histologic evaluation of quartz dust-exposed lungs showed alveolitis, including microgranulomas, which were associated with clusters of dust-containing macrophages and polymorphonuclear cells which were localized within alveoli and interstitium surrounding small bronchioles. The anthracite dust-exposed lungs contained similar cell types localized around small bronchioles, which did not form microgranulomas. Surfactant protein-A was found within alveolar type II cells and macrophages of both rat and primate lungs, but not within macrophages markedly distended with dust particles. The number of alveolar type II cells appeared to increase in response to the length of time of exposure to dust, as did the total amount of protein recovered in the surfactant-enriched fractions prepared from CF-BAL from dust-instilled lungs relative to that in surfactant-enriched fractions isolated from CF-BAL from control lungs.