Patterns of epoxide metabolism by epoxide hydrolase and glutathione S-transferase associated with age and genotype in Drosophila melanogaster

Epoxide hydrolase and glutathione S-transferase activities toward trans- and cis-stilbene oxides were measured in 3 strains of Drosophila melanogaster. Differences in age dependence, substrate selectivity and subcellular location were detected suggesting the presence of multiple forms of these enzymes. In addition, interstrain differences indicate the presence of genetic variation for epoxide hydrolase and glutathione transferase activities. These results illustrate a potential use of these assays in D. melanogaster to complement existing tests (e.g. recessive lethal tests or Ames assays) for evaluating the relationship between epoxide hydrolase and glutathione S-transferase levels and the genotoxicity of epoxides.

The influence of hemolymph-binding protein on juvenile hormone stability and distribution in Manduca sexta fat body and imaginal discs in vitro

The wing discs and fat body of Manduca sexta larvae contain enzymes (i.e. carboxylesterase and epoxide hydratase) that can convert the C18 juvenile hormone (JH) to the acid, diol and acid diol. No evidence of oxidative degradation was noted. In vitro studies suggest that JH can be compartmentalized within the cells of the fat body where it is less accessible to degradative mechanisms. Experiments utilizing a hemolymph-binding protein fraction (BPF) in vitro with fat body and imaginal discs indicate that the BPF retards the uptake of JH by tissues and its subsequent degradation by tissue enzymes. BPF also appears to protect JH from degradation by enzymes released into the medium. By these mechanisms the insect can maintain elevated JH titers for relatively long periods. Binding protein may also keep JH in solution in the hemolymph allowing its rapid distribution throughout the insect. The data suggest that the binding protein plays a key role in maintaining juvenile hormone titers.