[M-ZZ51] 環境汚染・環境毒性と生物

[MZZ51-P03] Evaluation of anticoagulant rodenticides (ARs) sensitivity in sea turtles

*中山 翔太^1,2、山村 快哉^1,3、近藤 理美⁴、北山 千代⁴、一瀬 貴大¹、池中 良徳^1,5,6,7、石塚 真由美¹ (1.北海道大学大学院獣医学研究院、2.ザンビア大学獣医学部、3.一般財団法人残留農薬研究所、4.Everlasting Nature of Asia (ELNA)、5.Water Research Group, School of Environmental Sciences and Development, North-West University, Private Bag X6001, Potchefstroom 2531, South Africa、6.Translational Research Unit, Veterinary Teaching Hospital, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan、7.One Health Research Center, Hokkaido University, Sapporo 060-0818, Japan)

キーワード：抗凝血系殺鼠剤、化学物質感受性、動物種差

Rodents such as black rats (Rattus rattus) and Norway rats (Rattus norvegicus) have been artificially introduced to islands many times, where they have generally caused severe damage to native ecosystems. Although anticoagulant rodenticides (ARs) are effectively used for the elimination of invasive rodents, nontarget species are also frequently exposed to ARs and secondary poisonings occur widely. However, little data is available on the effects of ARs, especially on marine organisms. To evaluate the effects of ARs on aquatic ecosystems, we chose green sea turtles (Chelonia mydas), which are one of the most common marine organisms around the Ogasawara islands, japan as our primary study species. The sensitivity of these turtles to ARs was assessed using both in vivo and in vitro approaches. We administered 4 mg/kg of warfarin sodium either orally or intravenously to juvenile green sea turtles. The turtles exhibited slow pharmacokinetics, and extension of prothrombin time (PT) was observed only with intravenous warfarin administration. This result indicates that in the green sea turtles, most of the warfarin administered orally was not absorbed, or it took a long time to be distributed throughout the body. We also conducted an in vitro investigation using liver microsomes from two other turtle species (softshell turtle and red-eared slider) and rats, as well as green sea turtles. The cytochrome P450 metabolic activity in the liver was lower than in rats. Additionally, vitamin K epoxide reductase (VKOR), which is the target enzyme of ARs, was inhibited by warfarin in the turtles at lower or similar concentration levels as in rats. These data indicate that turtles may be more sensitive to ARs than rats. In addition, we observed interspecific differences in warfarin metabolism among the three turtle species we studied. Vmax/Km values were higher in the red-eared sliders than in the Chinese softshell turtles or green sea turtles. This result indicates that red-eared sliders have a greater detoxification capacity when warfarin is present in concentrations that are physiologically tolerated. In conclusion, we expect that these findings will be helpful for sea turtle conservation following accidental AR-broadcast incidents.