Increased production and/or secretion of pulmonary surfactant in rats by long term sulfur dioxide exposure.

Influence of long term SO2 exposure on the pulmonary surfactant in rats was studied by means of chemical analysis and microscopic verification. At a time after termination of the exposure period, the general symptom in rats was similar to that of bronchitis. The content of disaturated phosphatidylcholine, a main functional component of the pulmonary surfactant, significantly increased not only in broncho-alveolar lavage fluid but also in pulmonary microsomal fraction by long term SO2 exposure. Microscopic verification of alveolar type II cells from the bronchitic rats demonstrated the development of rough surface endoplasmic reticulums and an increase of the number of osmiophillic bodies. The results suggest that pulmonary surfactant production and/or secretion are activated in rats with bronchitis caused by long term SO2 exposure.