Tissue-specific bioaccumulation, metabolism and excretion of tris (2-ethylhexyl) phosphate (TEHP) in rare minnow (Gobiocyprisrarus)

Rui Hou; Yiping Xu; Kaifeng Rao; Chenglian Feng; Zijian Wang

doi:10.1016/j.envpol.2020.114245

Tissue-specific bioaccumulation, metabolism and excretion of tris (2-ethylhexyl) phosphate (TEHP) in rare minnow (Gobiocyprisrarus)

Environ Pollut. 2020 Jun:261:114245. doi: 10.1016/j.envpol.2020.114245. Epub 2020 Feb 21.

Authors

Rui Hou¹, Yiping Xu², Kaifeng Rao³, Chenglian Feng⁴, Zijian Wang⁵

Affiliations

¹ Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China.
² Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China. Electronic address: ypxu@rcees.ac.cn.
³ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
⁴ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
⁵ State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.

PMID: 32220757
DOI: 10.1016/j.envpol.2020.114245

Abstract

Tris (2-ethylhexyl) phosphate (TEHP) is one of the most commonly used organophosphorus flame retardant (OPFR) analogues and is commonly detected in surface water and sediments. Limited information is available about the metabolic pathway or metabolite formation related to TEHP in fish. In this study, rare minnows (Gobiocyprisrarus) were exposed to TEHP in static water for 30 d to investigate the bioaccumulation and metabolite distribution in the fish muscle, liver, kidney, gill, GI-tract, ovary and testis. Based on the estimated k_up,_parent and k_d,parent values, the bioconcentration factors (BCF_parent) of TEHP in fish tissues were calculated in the order of kidney > ovary ≈ liver ≈ testis > gill ≈ GI-tract > muscle; this finding was consistent with the results of our previous study on other alkyl-substituted OPFRs. In addition, this study identified the metabolic profiles of TEHP in the liver. TEHP was oxidatively metabolized by the fish to a dealkylated metabolite (di 2-ethylhexyl phosphate; DEHP) and hydroxylated TEHP (OH-TEHP). OH-TEHP further underwent extensive phase II metabolism to yield glucuronic acid conjugates. DEHP was mainly distributed in rare minnow in the following order: liver > GI-tract > kidney ≫ other tissues. However, the metabolite showed lower accumulation potential in fish tissues than TEHP, with metabolite parent concentration factors (MPCFs) for DEHP of less than 0.1 in all the investigated tissues. The BCF_parent values of TEHP in various fish tissues were only 9.0 × 10^-3-7.2 × 10^-4 times its estimated tissue-water partition coefficient (K_tissue-water) values based on tissue lipid, protein and water contents, which indicated the significance of biotransformation in reducing the bioaccumulation potential of TEHP in fish. The toxicokinetic data in the present study help in understanding the tissue-specific bioaccumulation and metabolism pathways of TEHP in fish and highlight the importance of toxicology research on TEHP metabolites in aquatic organisms.

Keywords: Bioaccumulation; In vivo metabolism; Metabolite parent concentration factor; Toxicokinetic; Tris (2-ethylhexyl) phosphate (TEHP).

MeSH terms

Animals
Bioaccumulation
Cyprinidae* / metabolism
Female
Male
Organophosphates* / metabolism
Tissue Distribution
Water Pollutants, Chemical* / metabolism

Substances

Organophosphates
Water Pollutants, Chemical
tris(2,3-dibromopropyl)phosphate