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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Imported Fire Ant and Household Insects Research » Research » Publications at this Location » Publication #66316
Title: TISSUE LOCALIZATION, INDUCTION, AND DEVELOPMENTAL EXPRESSION OF CYTOCHROME P450 MONOOXYGENASES IN THE COCKROACH

Author
item Valles, Steven
item YU, SIMON - UNIV. OF FLORIDA

Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The development of insecticide resistance by the German cockroach prevents effective control of this pest. One of the major mechanisms responsible for insecticide resistance in insects is enhanced detoxification of the insecticide. To study this resistance mechanism, a thorough understanding of detoxification enzymes is necessary. Therefore, we have identified the major German cockroach insect tissues that contain these enzymes, when they are expressed in the German cockroach development cycle, and whether or not their expression is altered by foreign compounds German cockroaches may encounter. This information provides the necessary groundwork for future investigations into detoxification enzymes and their contribution to the insecticide resistance phenomenon in the German cockroach.

Technical Abstract: Methods of microsome preparation were evaluated to determine their influence on the activity of cytochrome P450 monooxygenases in adult males and final instar nymphs of the German cockroach, Blattella germanica (L.). Aldrin epoxidase activity was significantly improved when homogenization occurred in a protected buffer and when alimentary canal contents were removed prior to homogenization. Apparently, a potent inhibitor of cytochrome P450 monooxygenases, but not of cytochrome c reductase, is present in the gut contents of German cockroaches. Aldrin epoxidase and methoxyresorufin (MR) O-demethyla midgut, hindgut, Malpighian tubules, fat body, and the remaining tissues of the carcass) from adult males and final instar nymphs. Adult male aldrin epoxidase activity was highest in midgut and Malpighian tubules, while no single tissue dominated in MR O-demethylase ac cspecific activity was 9- to 11-fold higher in midgut than in fat body, while MR O-demethylase specific activity was 17- to 22-fold higher in fat body than in midgut. In the final instar, aldrin epoxidase, MR O-demethylase, ethoxyresorufin (ER) O-deethylase, and cytochrome c reductase activities were lowest at the time of ecdysis and highest near the middle of the stadium. Dietary phenobarbital at the 0.2% level induced various microsomal oxidases including aldrin epoxidase, MR O-demethylase, ER O-deethylase, and cytochrome c reductase in final instar nymphs and adults.