The effects of 2-ethylhexyl diphenyl phosphate (EHDPP) on cytotoxicity and mRNA expression, as well as its metabolism, were investigated using a chicken embryonic hepatocyte (CEH) assay. After incubation for 36 h, the lethal concentration 50 (LC50) was 50 ± 11 μM, suggesting that EHDPP is one of a small cohort of highly toxic organophosphate esters (OPEs). By use of a ToxChip polymerase chain reaction (PCR) array, we report modulation of 6, 11, or 16/43 genes in CEH following exposure to 0.1, 1, or 10 μM EHDPP, respectively. The altered genes were from all nine biological pathways represented on the ToxChip including bile acids/cholesterol regulation, glucose metabolism, lipid homeostasis, and the thyroid hormone pathway. After incubation for 36 h, 92.5% of EHDPP was transformed, and one of its presumed metabolites, diphenyl phosphate (DPHP), only accounted for 12% of the original EHDPP concentration. Further screening by use of high-resolution mass spectrometry revealed a novel EHDPP metabolite, hydroxylated 2-ethylhexyl monophenyl phosphate (OH-EHMPP), which was also detected in a human blood pool. Additional EHDPP metabolites detected in the human blood pool included EHMPP and DPHP. Overall, this study provided novel information regarding the toxicity of EHDPP and identified a potential EHDPP metabolite, OH-EHMPP, in both avian species and humans.

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Journal Environmental Science and Technology
Shen, J. (Jinyou), Zhang, Y. (Yayun), Yu, N. (Nanyang), Crump, D. (Doug), Li, J. (Jianhua), Su, H. (Huijun), … Su, G. (Guanyong). (2019). Organophosphate Ester, 2-Ethylhexyl Diphenyl Phosphate (EHDPP), Elicits Cytotoxic and Transcriptomic Effects in Chicken Embryonic Hepatocytes and Its Biotransformation Profile Compared to Humans. Environmental Science and Technology, 53(4), 2151–2160. doi:10.1021/acs.est.8b06246