Regulation of cytochrome P-450 dependent steroid hydroxylase activity in Manduca sexta: effects of the ecdysone agonist RH 5849 on ecdysone 20-monooxygenase activity.
The non-steroidal ecdysone agonist RH 5849 (1,2-dibenzoyl-1-tert-butylhydrazine) was found to inhibit in a dose-response and apparently competitive fashion the cytochrome P-450 dependent ecdysone 20-monooxygenase activity in the midgut of wandering stage last instar larvae of the tobacco hornworn, Manduca sexta. More effectively on a per molar basis than the naturally occurring molting hormones ecdysone and 20-hydroxyecdysone, RH 5849 was also found to elicit the dramatic 50-fold increase in midgut steroid hydroxylase activity (which normally occurs with the onset of the wandering stage) when injected into competent head or thoracic ligated pre-wandering last instar larvae. These data support and extend the potential usefulness of RH 5849 as a pharmacological probe for further investigating the actions of ecdysteroids and their role(s) in the regulation of ecdysteroid monooxygenases.
Keogh
D P
DP
Department of Biological Sciences, Bowling Green State University, OH 43403.
Smith
S L
SL
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004064:Digestive System / Q000201:enzymology; D006834:Hydrazines / Q000494:pharmacology*; D007306:Insecticides / Q000494:pharmacology*; D007700:Kinetics; D007814:Larva; D009036:Moths / Q000201:enzymology*; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors*
D006834:Hydrazines; D007306:Insecticides; C056565:1,2-dibenzoyl-tert-butylhydrazine; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C020095:ecdysone 20-hydroxylase