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Abstract: Polybrominated diphenyl ethers (PBDEs) are now found ubiquitously in the aquatic environment and biota, and there is a growing concern that PBDEs may disrupt endocrine systems, leading to reproductive impairments of aquatic animals. In our study, zebrafish (Danio rerio) were exposed to the 5ng/L, 1μg/L and 50μg/L of DE-71 for the duration of the whole life cycle (120days, from eggs to adults). The expression of selected genes along the brain–pituitary–gonadal (BPG) axis and liver, and the levels of plasma sex hormones were examined. In male fish, up-regulation of GnRH in brain, FSHβ and LHβ in pituitary, FSH-receptor, LH-receptor, and CYP19a in testis was clearly evident, while down-regulation of CYP11a and 3β-HSD was found in testis. In female fish, a 2.4-fold up-regulation of 3β-HSD was found in ovary upon exposure to 50μg/L of DE-71. GnRH in brain, FSHβ and LHβ in pituitary were also up-regulated, while ERβ, TH and TPH in brain and GnRH-receptor in pituitary were significantly down-regulated. Hepatic ERα, AR and VTG in males were all down-regulated, while hepatic ERα and AR in female were up-regulated. Serum estradiol (E2) was reduced in both male and female upon exposure to DE-71, while significant increases in serum testosterone (T) and 11-keto-testosterone (11-KT) were only found in male but not female fish. The ratio of T/E2 as well as the ratio of 11-KT/E2 in male fish increased in a dose-dependent manner upon exposure to DE-71. Our overall results showed that whole life exposure of DE-71 altered the expression of regulatory genes and receptors at all three levels of the BPG axis in zebrafish, and the responses are sex dependent. The observed disruption of GnRH and GtHs can be further related to the subsequent disruption in both levels and balance sex steroid hormones. [Copyright &y& Elsevier]

Abstract: Sediments and green-lipped mussels, Perna viridis, were used to investigate concentrations of polybrominated diphenyl ethers (PBDEs) in Hong Kong’s marine environment. PBDEs have been used extensively over the past two decades as flame retardants in polymer additives for a variety of plastics, computers, furniture, building materials, and fabrics. Many measurements of PBDEs in various environmental matrices have been reported from Belgium, Holland, Japan, Europe and North America, but few measurements are available for the southeast Asian region and Hong Kong. PBDE congeners (n =15) were measured in 13 sediments and nine mussel samples, taken from Hong Kong marine waters. The in sediments ranged between 1.7 and 53.6ngg−1 dry wt, with the highest concentrations located around the most heavily populated areas of Victoria Harbour and Sai Kung, while the lowest concentrations of were found at more remote locations of Sha Tau Kok, Wong Chuk Bay, Castle Peak Bay, and Gold Coast. ranged from 27.0 to 83.7ngg−1 dry wt of mussel tissues. Although not identical, most of the congeners in sediments were found in mussel tissues, with BDE-47, BDE-99, BDE-153 and BDE-183 being the most prominent in both matrices. On the basis of a literature survey, the concentrations of PBDEs reported in Hong Kong sediments and mussel tissues are amongst the highest in the world. [Copyright &y& Elsevier]

Abstract: The bioaccumulation and maternal transfer of 2,2′,4,4′-tetrabromodiphenyl ether (PBDE 47) were investigated in the marine medaka (Oryzias melastigma) following dietary exposure, in which PBDE 47 was bioencapsulated into brine shrimp (Artemia sp.) and fed daily to male-female pairs of medaka. In the accumulation experiment, each 2-month-old (pre-breeding) medaka were provided with dietary PBDE 47 at 1.3±0.2μg/day for 21days. Growth-corrected concentrations of PBDE 47 in the medaka increased over the 21days of exposure and there were no significant differences between males and females at any of the sampling times. Final concentrations were similar for males and females after 21days (230±30 and 250±30μgg−1 wet weight, respectively), accounting for 84–100% of the PBDE 47 provided in the diet. In the maternal transfer experiment, 3-month-old (breeding) medaka were provided with dietary PBDE 47 at 1.2±0.2μg/day for 18days, and reached body concentrations of 76±3 (males) and 61±6 (females)μgg−1 wet weight. Female growth-corrected PBDE 47 concentrations were significantly lower than males by day 12 (P <0.05), and egg PBDE 47 concentrations were up to 25ng/egg by day 18. Our results showed that maternal transfer is an important offloading mechanism for female fish. The fact that lipid normalized egg:female PBDE ratios did not significantly deviate from 1 further indicated that the maternal transfer of PBDE 47 is associated with lipid mobilization during egg production. [Copyright &y& Elsevier]

Abstract: Polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA) are brominated flame retardants that are produced in large quantities and are commonly used in construction materials, textiles, and as polymers in electronic equipment. Environmental and human levels of PBDEs have been increasing in the past 30 years, but the toxicity of PBDEs is not fully understood. Studies on their effects are relatively limited, and show that PBDEs are neurotoxins and potential endocrine disrupters. Hydroxylated (OHhoxylated (MeOave also been reported in the adipose tissue, blood and milk of wild animals and humans. In the present study, 15 PBDE metabolites, two BDE mixtures (DE71 and DE79), and TBBPA were studied individually to determine their effects on ten steroidogenic genes, aromatase activity, and concentrations of two steroid hormones (testosterone and 17β-estradiol) in the H295R human adrenocortical carcinoma cell line. Exposure to 0.05μM 2′-OH-BDE-68 significantly induced the expression of CYP11A, CYP11B2, CYP17, CYP21, 3βHSD2, 17βHSD1, and 17βHSD4, and the expression of StAR was induced by 6-OH-BDE-90 at the three exposure concentrations. Exposure to DE71 and DE79 resulted in dose-dependent trend towards induction, but these effects were not significant. Exposure to 0.5μM 2-OH-BDE-123 and 2-MeO-BDE-123 resulted in significantly greater aromatase activity. However, none of the compounds affected sex hormone production at the concentrations tested. Generally, OH-BDEs had a much stronger ability to affect steroidogenic gene expression than MeO-BDEs. [Copyright &y& Elsevier]