Identification of multiple steroid hydroxylases in Daphnia magna and their modulation by xenobiotics
- North Carolina State Univ., Raleigh, NC (United States). Dept. of Toxicology
Steroid hydroxylase activities were characterized in Daphnia magna and evaluated for potential use as biomarkers of xenobiotic exposure. Microsomes prepared from Daphnia magna generated as single NADPH-dependent metabolite of [[sup 14]C] testosterone. However, intact daphnids excreted at least 10 polar metabolites of [[sup 14]C] testosterone into the test medium. Six of these metabolites were identified as 2[alpha]-, 16[beta]-, 6[beta]-, 6[alpha]-, 7[alpha]-, and 15[alpha]-[[sup 14]C]hydroxytestosterone. The unidentified metabolites are also presumed to be hydroxylated products of testosterone, based on their relative migrations during TLC. The inefficient metabolism of [[sup 14]C] testosterone during the in vitro microsomal incubations may have been due to the release of P450 inhibitors during microsome preparation. Exposure of daphnids to the P450 modulators phenobarbital, [beta]-naphthoflavone, piperonyl butoxide, and malathion differentially inhibited the steroid hydroxylase activities. Results from this study indicate that Daphnia magna expresses several P450 enzymes and that these enzymes are differentially modulated by xenobiotic exposure. Steroid hydroxylase activities may serve not only as a biomarker of toxicant exposure, but also as a predictor of toxicant effects involving perturbations of steroid hormone homeostasis.
- OSTI ID:
- 7264992
- Journal Information:
- Environmental Toxicology and Chemistry; (United States), Journal Name: Environmental Toxicology and Chemistry; (United States) Vol. 13:7; ISSN ETOCDK; ISSN 0730-7268
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANDROGENS
ANDROSTANES
ANIMALS
AQUATIC ORGANISMS
ARTHROPODS
BIOLOGICAL MARKERS
BRANCHIOPODS
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CRUSTACEANS
DAPHNIA
ENZYME ACTIVITY
ENZYMES
HORMONES
HYDROXY COMPOUNDS
HYDROXYLASES
INVERTEBRATES
ISOTOPE APPLICATIONS
KETONES
LABELLED COMPOUNDS
METABOLISM
ORGANIC COMPOUNDS
OXIDOREDUCTASES
POLLUTION
PROTEINS
SENSITIVITY
STEROID HORMONES
STEROIDS
TESTOSTERONE
TRACER TECHNIQUES
WATER POLLUTION
XENOBIOTICS