Toxaphene detoxification and acclimation in Daphnia magna: do cytochrome P-450 enzymes play a role?
Toxaphene is a persistent environmental contaminant that has been shown to alter male production in Daphnia magna and to induce P-450 activity in mammals. Cytochrome P-450-mediated metabolism may lead to xenobiotic detoxification resulting in acclimation. To determine if D. magna acclimate to toxaphene via P-450 pathways, chronic and acute toxicity tests were conducted with D. magna exposed to toxaphene in the presence and absence of piperonyl butoxide (PBO), an inhibitor of cytochrome P-450 enzymes. Toxaphene exposure increased male production in acute but not chronic assays, indicating that D. magna may acclimate to chronic toxaphene exposure. Upon co-administration of toxaphene and PBO in chronic tests, D. magna exhibited a decline in growth rate, fecundity and survival. The observed toxaphene acclimation in chronic tests, along with its increased toxicity in the presence of a P-450 suppressor, suggests that P-450 enzymes may contribute to detoxification and subsequent acclimation of D. magna to chronic toxaphene exposure. Additional chronic toxicity tests indicated that toxaphene acclimation occurs between 7 and 12 days following initial exposure, at which time sex determination is no longer affected. Thus, sublethal toxaphene toxicity effects such as reproductive impairments may be detectable with acute but not chronic tests, potentially due to the upregulation of P-450 isozymes.
Department of Fisheries and Wildlife Biology, Colorado State University, 136 JVK Wagar Building, Fort Collins, CO 80523-1474, USA. dkashian@cnr.colostate.edu
Donna R
DR
Kashian
D000064:Acclimatization / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003621:Daphnia / Q000201:enzymology / Q000378:metabolism* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000633:toxicity; D005260:Female; D005298:Fertility / Q000187:drug effects; D008658:Inactivation, Metabolic; D007306:Insecticides / Q000493:pharmacokinetics* / Q000633:toxicity; D008297:Male; D010574:Pesticide Synergists / Q000494:pharmacology / Q000633:toxicity; D010882:Piperonyl Butoxide / Q000494:pharmacology / Q000633:toxicity; D012744:Sex Ratio; D014112:Toxaphene / Q000493:pharmacokinetics* / Q000633:toxicity; D023382:Toxicity Tests, Acute; D036401:Toxicity Tests, Chronic
D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D007306:Insecticides; D010574:Pesticide Synergists; D014112:Toxaphene; D003577:Cytochrome P-450 Enzyme System; D010882:Piperonyl Butoxide