J. Biol. Chem., Vol. 256, Issue 19, 9994-9998, Oct, 1981
Paraquat and NADPH-dependent lipid peroxidation in lung microsomes
HP Misra and LD Gorsky
Since there exists some controversy in the literature as to whether
paraquat augments microsomal lipid peroxidation via superoxide anion (O2-),
the role of paraquat and active oxygen species in NADPH- dependent lung
microsomal lipid peroxidation was investigated. Incubation of buffered
aerobic mixture of bovine lung microsome and NADPH, in the presence or
absence of exogenously added iron, resulted in a progressive formation of
lipid peroxides whose accumulation could be followed at 535 nm as
malondialdehyde. Paraquat strongly inhibited this lipid peroxidation. Thus,
malondialdehyde formation was 50% inhibited by 4 X 10(-5) M paraquat in the
reaction mixture. The malondialdehyde color development by lipid peroxides
was not affected by this concentration of paraquat. Lipid peroxidation was
also strongly inhibited by singlet oxygen scavengers, e.g. dimethylfuran
and diphenylfuran, and by catalase. Hydroxyl radical scavengers, e.g.
mannitol, benzoate, and ethanol, had little effect in malondialdehyde
production. Superoxide dismutase, which removes O2- efficiently, did not
inhibit malondialdehyde production by lung microsomes and rather enhanced
its formation. A scheme in which paraquat and active O2 species may be
involved with microsomal lipid peroxidation is presented.
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