title: Cytochemical energy-filtering transmission electron microscopy of mitochondrial free radical formation in paraquat cytotoxicity.
abstract: The generation of oxygen free radicals was investigated using cytochemistry and its energy-filtering transmission electron microscopy in reference to the toxic mediator for the herbicide paraquat. When isolated intact mitochondria from rat livers were incubated in a medium containing paraquat and NADH, a mitochondrial NADH-quinone oxidoreductase activity generated superoxide anions to cause the destruction of mitochondria which resulted in cell death. The superoxide anions were immediately converted into hydrogen peroxide, which then formed cerium perhydroxide deposits in the presence of cerium ions and precipitated on the outer surface of the mitochondrial outer membrane. This localization was also specifically identified by energy spectral imaging and image-electron energy loss spectral analyses. Precipitation reaction was scavenged by the addition of either cytochrome c or catalase and inhibited by dicoumarol (an inhibitor of NAD(P)H-quinone oxidoreductases). These cytochemical energy-filtering transmission electron microscopic results indicated that paraquat generated free radicals from the outer membrane of mitochondria.
authors.affiliation: Department of Anatomy and High-Technology Research Center, Kanazawa Medical University, Japan. keih@kanazawa-med.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Hirai
authors.forename: J
authors.initials: J
authors.lastname: Pan
authors.forename: H
authors.initials: H
authors.lastname: Shimada
authors.forename: T
authors.initials: T
authors.lastname: Izuhara
authors.forename: T
authors.initials: T
authors.lastname: Kurihara
authors.forename: K
authors.initials: K
authors.lastname: Moriguchi
mesh_terms: D000818:Animals; D003470:Culture Media; D005609:Free Radicals / Q000378:metabolism; D006651:Histocytochemistry; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron / Q000379:methods*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D010269:Paraquat / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D003470:Culture Media; D005609:Free Radicals; D006861:Hydrogen Peroxide; D016660:NAD(P)H Dehydrogenase (Quinone); D010269:Paraquat