Mitochondrial breakage induced by the herbicide paraquat in cultured human lung cells

Although the intracellular toxic sites of paraquat, a herbicide toxic to human bodies, have remained unclear for a long time, we recently demonstrated paraquat-induced mitochondrial injury in rat lung and liver in vivo. In the present study, cultured human lung cells (A549 adenocarcinoma cell line) which received 0.15 mM paraquat (equivalent to 40 mg/kg i.v.) showed selective mitochondrial breakage at 6-24 hr and died at 36-48 hr. These results suggest that mitochondria are the initial toxic site of paraquat in vitro as well as in vivo in contrast to the previously proposed microsome theory.