The Journal of Toxicological Sciences
Online ISSN : 1880-3989
Print ISSN : 0388-1350
ISSN-L : 0388-1350
Original Article
Developmental changes in drug-metabolizing enzyme expression during metamorphosis of Xenopus tropicalis
Junpei MoriSeigo SanohKeiko KashiwagiHideki HanadaMitsuki ShigetaKen-ichi T. SuzukiTakashi YamamotoYaichiro KotakeKazumi SugiharaShigeyuki KitamuraAkihiko KashiwagiShigeru Ohta
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Supplementary material

2017 Volume 42 Issue 5 Pages 605-613


A large number of chemicals are routinely detected in aquatic environments, and these chemicals may adversely affect aquatic organisms. Accurate risk assessment requires understanding drug-metabolizing systems in aquatic organisms because metabolism of these chemicals is a critical determinant of chemical bioaccumulation and related toxicity. In this study, we evaluated mRNA expression levels of nuclear receptors and drug-metabolizing enzymes as well as cytochrome P450 (CYP) activities in pro-metamorphic tadpoles, froglets, and adult frogs to determine how drug-metabolizing systems are altered at different life stages. We found that drug-metabolizing systems in tadpoles were entirely immature, and therefore, tadpoles appeared to be more susceptible to chemicals compared with metamorphosed frogs. On the other hand, cyp1a mRNA expression and CYP1A-like activity were higher in tadpoles. We found that thyroid hormone (TH), which increases during metamorphosis, induced CYP1A-like activity. Because endogenous TH concentration is significantly increased during metamorphosis, endogenous TH would induce CYP1A-like activity in tadpoles.

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© 2017 The Japanese Society of Toxicology
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