Dose-dependent effects of flufenoxuron on thyroid system of mature female lizards (Eremias argus) and their offspring

Abstract

More and more studies are focusing on toxic effect of pesticides on lizards. However, the responses of different life-stage lizards to pesticides have not been reported. In this study, according to RNA-seq library data, thyroxine 5′-deiodinase activity showed significant difference between mature and immature lizard liver. In addition, triiodothyronine (T3) level in immature lizard serum was higher than that in mature lizard serum. Thus, we investigated the thyroid disruption of flufenoxuron with different concentrations (0, 5, 20 mg/kg) to both mature lizards and their offspring. No significant differences were observed in immature lizard body weight compared between control and exposure groups while the body weight of mature lizards was significantly decreased after flufenoxuron exposure. Moreover, the levels of thyroid hormones and the expression of thyroid related genes changed with exposure concentration of flufenoxuron and exhibited different regulation mechanism between mature and immature lizards. In immature lizard liver, trα, trβ, dio1 and ugt genes controlled the thyroid hormone levels interfered by flufenoxuron. In contrast, the thyroxine (T4) pathway in mature lizard liver was significantly disrupted especially by 20 mg/kg flufenoxuron exposure. This study elucidated the different thyroid disruption effects of flufenoxuron to lizards based on different exposure doses and lizard life stages.