Triphenyl Phosphate at Environmental Levels Retarded Ovary Development and Reduced Egg Production in Japanese Medaka (Oryzias latipes)

Since triphenyl phosphate (TPhP) elicits both anti-estrogenic activity via blocking estrogen receptor (ER) and estrogenic activity by elevating 17β-estradiol (17β-E2) synthesis, its adverse effects on female reproduction is uncertain. In this study, we exposed Japanese medaka to TPhP at 131, 363, and 1773 ng/L for 100 days following hatching. TPhP significantly induced ovary retardation in all exposure groups (incidence: from 11.9% to 37.8%) and reduced egg production by 38.9% and 50.9% in the 363 and 1773 ng/L exposure groups, respectively. Vitellogenin (vtg) transcription was significantly down-regulated by 35.4-57.4% after TPhP exposure, explaining the ovary retardation. Considering 17β-E2 was only significantly decreased in 1773 ng/L exposure group, ER antagonism could be the dominant contributor to the inhibition of vtg transcription and female reproductive toxicity of TPhP. As 4-hydroxyphenyl diphenyl phosphate, a metabolite of TPhP, was detected in livers with similar concentration [68.4-1237 ng/g ...