Enhancement by cyanide of aniline p-hydroxylation activity in rat liver microsomes

Phenobarbital-induced rat liver homogenate and microsomes were used to study covalent binding of 14C-labelled (at the alcohol moiety) cismethrin, 14C-labelled (at the alcohol and acid moieties) cypermethrin, and 14C-labelled (at the alcohol and acid moieties) deltamethrin. Covalent binding was dependent on pyrethroid concentration. With liver homogenate, inhibition of esterases by tetraethylpyrophosphate and of mitochondrial respiration by rotenone or potassium cyanide only slightly altered the covalent binding level. With microsomes, inhibition of cytochrome P-450 and mixed function oxidases by carbon monoxide and piperonyl butoxide reduced the covalent binding so far as to be nearly absent. Eighty percent inhibition of epoxide hydrolase decreased the covalent binding by 50%. The comparison of data between alcohol and acid labelling of the same pyrethroid suggested that, in vitro, the whole molecule is bound to proteins and that hydrolysis can occur afterwards. The experiments stress the role of cytochrome P-450-dependent monoxygenases in the covalent binding process.

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In vitro covalent binding of the pyrethroids cismethrin, cypermethrin and deltamethrin to rat liver homogenate and microsomes

Catinot

Hoellinger

Sonnier

et al. 1989

Arch Toxicol

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Effect of inhibitors on ω‐and (ω‐1)‐hydroxylation of lauric acid by frog liver microsomes

Miura

1982

Lipids

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To investigate the involvement of different cytochrome P-450 monooxygenases in fatty acid hydroxylation in frog liver microsomes, the effect of various inhibitors of cytochrome P-450 monooxygenases on the omega- and (omega-1)-hydroxylation of laurate was examined. The omega/omega-1-hydroxylation ratios were changed significantly by various levels of carbon monoxide (CO) inhibition; the formation of omega-hydroxylaurate was more sharply inhibited by various levels of CO than was the formation of (omega-1)-hydroxylaurate. On the contrary, metyrapone inhibited only the formation of (omega-1)-hydroxylaurate and stimulated the formation of omega-hydroxylaurate, 7,8-Benzoflavone as well as CO was more inhibitory to the omega-hydroxylation of laurate. At low concentrations of KCN (0.2 and 0.1 mM), the (omega-1)-hydroxylase activity was stimulated, but both the omega- and (omega-1)-hydroxylase activities were inhibited at the higher concentrations (5-10 mM). The effect of drugs and hydroxylaurate isomers on the omega- and (omega-1)-hydroxylation was also examined. Aminopyrine showed a stimulative effect on omega-hydroxylase activity and no effect on the (omega-1)-hydroxylase activity, while p-nitroanisole inhibited the (omega-1)-hydroxylase activity and showed almost no effect on the omega-hydroxylase activity. 12-Hydroxylaurate inhibited both the omega- and (omega-1)-hydroxylase activities, but the omega-hydroxylase activity was inhibited to a much greater extent. 11-Hydroxylaurate had no effect on either hydroxylation. These findings strongly support the hypothesis that different cytochrome P-450 species are involved in the hepatic microsomal hydroxylation of laurate at omega- and (omega-1)-positions in the frog.

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In vivo effects of nitrogen dioxide on membrane constituents in lung and liver of rats

Mochitate

Kaya

Miura

et al. 1984

Environmental Research

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Enhancement by cyanide of aniline p-hydroxylation activity in rat liver microsomes

Cited by 8 publications

References 44 publications

In vitro covalent binding of the pyrethroids cismethrin, cypermethrin and deltamethrin to rat liver homogenate and microsomes

In vitro covalent binding of the pyrethroids cismethrin, cypermethrin and deltamethrin to rat liver homogenate and microsomes

Effect of inhibitors on ω‐and (ω‐1)‐hydroxylation of lauric acid by frog liver microsomes

In vivo effects of nitrogen dioxide on membrane constituents in lung and liver of rats

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