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In vivo and in vitro metabolism of fipronil by larvae of the European corn borer Ostrinia nubilalis
Author(s) -
Durham Eric W,
Siegfried Blair D,
Scharf Michael E
Publication year - 2002
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.523
Subject(s) - ostrinia , piperonyl butoxide , fipronil , european corn borer , metabolite , in vivo , monooxygenase , midgut , biology , microsome , biochemistry , metabolism , sulfone , pyralidae , cytochrome p450 , chemistry , in vitro , botany , larva , pesticide , microbiology and biotechnology , agronomy , polymer chemistry
In vivo and in vitro metabolism of [ 14 C]fipronil was examined in a susceptible European corn borer ( Ostrinia nubilalis , Hübner) laboratory strain. [ 14 C]Fipronil penetrated the larval integument slowly, with 71.5% of the applied radioactivity recovered from surface rinses 24 h after topical application. Despite this slow penetration, radioactivity was detected in both the excrement and internal organo‐soluble fractions. Radioactivity in the internal aqueous fraction and tissue pellet accounted for less than 0.8% of total radioactivity. The in vivo studies suggest that fipronil oxidation to its sulfone metabolite is the major route of metabolic conversion. In vitro studies were performed using subcellular microsomal fractions isolated from European corn borer larval midguts. Cytochrome P450‐dependent monooxygenase activity (methoxyresorufin O ‐demethylase) was consistently observed in midgut preparations, and formation and detection of the sulfone metabolite in the same midgut preparations was also NADPH‐dependent and inhibited by piperonyl butoxide. In vitro metabolism results indicate microsomal monooxygenases are responsible for the conversion of fipronil to its sulfone form in the European corn borer. © 2002 Society of Chemical Industry