CHARACTERIZATION OF MICROSOMAL OXIDATIVE ACTIVITIES IN A WILD-TYPE AND IN A DDT RESISTANT STRAIN OF DROSOPHILA-MELANOGASTER

Resistance of a laboratory selected DDT strain of Drosophila melanogaster (RalDDTR) has been found to be monofactorial and correlated to an increased level of activity of the cytochrome P450-dependent mixed function oxidase (MFO). Both strains metabolize DDT and deltamethrin via MFO activity. However, the resistant strain does it more rapidly. The amount of DDT metabolites, including kelthane, bis-4-chlorophenyl acid, bis-4-chlorophenyl-ethanol, and 1,1-bis (p-chlorophenyl)2,2-dichloroethane, is approximately 9-fold greater with RalDDTR microsomes than with the wild-type strain Raleigh (Ral). Production of deltamethrin metabolites is 2.7-fold higher within the resistant strain. As compared to insecticides, lauric acid and the two steroids used as substrates in this study present many more sites for MFO metabolic action. Lauric acid is hydroxylated on positions 11 and 12 by both strains, but the amount of metabolites formed is 10-fold higher with RalDDTR microsomes. The 2,22-dideoxyecdysone is converted to two polar metabolites when incubated with RalDDTR microsomal preparations. These unidentified metabolites are neither 2-deoxyecdysone nor ecdysone. Also reported for the first time is the metabolization of testosterone by insect microsomes, which gives 13 oxiderivatives formed at different rates, depending on the strains. © 1990.