Effect of diisobutyl adipate on the expression of biomarker genes that respond to endocrine disruption and on gonadal sexual differentiation in Japanese medaka (Oryzias latipes)

Abstract

Phthalate and non-phthalate plasticizers are used in polymer materials, such as plastic and rubber. Recently, it has been revealed that diisobutyl adipate (DIBA), which is considered an environmentally safe non-phthalate plasticizer, potentially disrupts thyroid hormone activity in fish. In this study, we determined the sexual hormone effects of DIBA by analyzing the changes in the expression levels of genes that respond to endocrine disruption and sexual hormone activity in the livers and gonads of Japanese medaka. Then, we investigated the effects of DIBA on gonadal sexual differentiation in Japanese medaka. Compared with the control group, the mRNA expression of chgH, vtg1, vtg2, and esr1 was significantly suppressed in the livers of XX individuals exposed to DIBA. Meanwhile, the mRNA expression of gsdf was significantly upregulated and downregulated in the gonads of XX and XY individuals, respectively, after DIBA exposure. The mRNA expression of esr1 and esr2b were significantly suppressed by DIBA exposure in the gonads of both XX and XY individuals. These data suggest that DIBA has potential androgenic activity in Japanese medaka. However, normal testes in XY medaka and ovaries in XX medaka were observed following DIBA exposure. These results suggest that DIBA may have weak androgenic activity.