[Morphology of 3,4,5,3',4'-pentachlorinated biphenyl-induced change in canine lung]

We investigated the light and electron microscopical changes of the lung in dogs treated with 3,4,5,3',4'-pentachlorinated biphenyl (PenCB). Beagle dogs were orally administered with 0.1 mg/kg of PenCB, and sacrificed 3, 5 and 7 weeks after the PenCB administration. Light microscopically, bronchiolar epithelial cells showed cytoplasmic vacuolization, which was most prominent 5 weeks after the PenCB administration. Electron microscopically, nonciliated bronchiolar epithelial cells (Clara cells) revealed degradation of glycogen particles, swollen, irregularly arranged smooth endoplasmic reticulum, and swollen mitochondria, while no significant change was found in other epithelial cells. The endothelial cells also showed no significant change except for increased number of cytoplasmic vesicles. This is a first report on halogenated hydrocarbon-induced degradation of glycogen particles in Clara cells.