Effects of subchronic exposure to a diisocyanate -MDI- on the pulmonary surfactant system and lung function.

Diisocyanates are known to induce pulmonary affections in exposed workers. Deterioration of the mechanical and immunological integrity of the deeper lung by inhaled toxicants may be caused by suppression of the pulmonary surfactant system. In order to evaluate pollutant-surfactant interactions adult female Wistar rats were exposed to 3.0 mg/cbm monomeric diphenylmethane-diisocyanate (MDI) for 4 weeks. Bronchoalveolar lavage fluid (BALF) was collected and surfactant phospholipid content determined by thin-layer chromatography. In a satellite group exposed for 6 weeks under identical conditions, mechanical lung function measurements were performed in a whole-body plethysmograph. Total phospholipid content of BALF was significantly reduced as well as the relative phosphatidylcholine content in the MDI group compared to the clean air group. The percentage of all other surfactant phospholipids was significantly increased with the phosphatidylserin/- inositol fraction showing the highest lev el of significance. There were no significant changes in dynamic and quasi-static lung compliance nor in lung resistance in the MDI group. These results suggest that the surfactant system is suppressed by inhalative exposure to MDI, but this suppression does not result in an impaired mechanical behaviour of the lung.