Lung surfactant and organelles after an exposure to dibenzoxazepine (CR).

Rats were exposed to a heavy dosage of the sensory irritant dibenz (b.f.)-1,4 oxazepine (CR). No change in the lung surfactant could be detected by the methods used. Electron micrography showed that the ordinary lamellated osmiophilic bodies (LOPBs) and their precursors were unaffected. Bodies containing both mitochondrial cristae and dense osmiophilic whorls (“mitochondrial lamellated bodies”, or MLBs) were found in the type II cells of some animals up to 15 days after the exposure. These whorls originate from the bounding membranes and cristae; serial sections show that they usually abut on the boundary of the organelle. A large proportion of the mitochondria in any cell may be affected by this process. Unequivocal evidence that the MLBs finally evolve into LOPBs without cristae was not obtained in this series; the ultimate fate of the MLBs and the cells containing them is uncertain. The MLBs may perhaps act as an emergency source of surfactant.