Browsing by Author "Zephyr, N."
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- Assessment of the mechanisms and pathways of fish contamination and mercury-selenium antagonismPublication . Ribeiro, M.; Zephyr, N.; Leufroy, A.; Coelho, I.; Danion, M.; Castanheira, I.; Guerin, T.; Jitaru, P.AIM Mercury (Hg) is one of the most dangerous chemical contaminants for humans and the environment. This is due to its extreme toxicity, particularly in the methylated form, denominated methylmercury (CH3Hg), which is easily absorbed by the body (bioaccumulation). CH3Hg is present in low concentrations in water and in water sediments, and can greatly increase its concentration in aquatic organisms, often reaching more than 85% of total Hg. Therefore, the main source of exposure to CH3Hg is fish consumption, in particular fish from higher trophic levels, since its content tends to increase along the food chain (biomagnification). Nevertheless, it is interesting to note that mercury´s bioavailability seems to be linked to selenium (Se) levels. The Se protective effects against Hg bioaccumulation and toxicity has been identified for the last decades, although the mechanism is still poorly understood. The aim of this study is to accurately assess the Hg-Se interaction in fish and the human dietary exposure. MATERIAL AND METHODS A bioassay was carried out in a representative freshwater fish (rainbow trout) in collaboration with the fish viral pathology unit of ANSES (Ploufragan-Plouzané laboratory). Fish were dietary exposed to CH3Hg under controlled conditions, in the presence or absence of SeMet. The final concentration of CH3Hg and SeMet in the diets was respectively 0,2 μg g-1 and 5 μg g-1. Briefly, six feeding protocols were compared: a non-supplemented diet (control group), a diet supplemented with SeMet, a diet supplemented with MeHg, a diet supplemented with both MeHg and SeMet, a diet supplemented first with MeHg for 1 month and then with SeMet for 2 months and a diet supplemented with SeMet for 1 month and then with MeHg for 2 months. The edible part of fish (muscle) was analysed for SeT and Hgt concentrations by ICP-MS after different time of exposure (1 month, 2 months and 3 months).
- Assessment of the mercury-selenium antagonism in rainbow trout fishPublication . Ribeiro, M.; Zephyr, N.; Silva, J.A.L.; Danion, M.; Guérin, T.; Castanheira, I.; Leufroy, A.; Jitaru, P.This study aims at the assessment of mercury (Hg)-selenium (Se) antagonism in fish. For this purpose, rainbow trout fish (Oncorhynchus mykiss) were exposed to methylmercury (MeHg) under controlled conditions, in the presence or absence of selenomethionine (SeMet) using an in-house prepared diet (enriched with MeHg and SeMet at 0.2 μg/g and 5.0 μg/g, respectively). The total duration of the exposure study was 3 months. Fish was sampled and analysed for total Se (SeT) and total mercury (HgT) content after 1, 2 and 3 months of exposure. Six feeding protocols were compared, depending on the exposure type: (i) no MeHg nor SeMet exposure (control group); (ii) exposure to SeMet solely; (iii) exposure to MeHg solely; (iv) exposure to both MeHg and SeMet; (v) exposure first to MeHg during 1 month and then to SeMet during 2 months and (vi), exposure to SeMet during 1 month and then to MeHg for 2 months. The levels of SeT and HgT in the fish (control and supplemented with MeHg/SeMet) were measured by inductively coupled plasma-mass spectrometry (ICPMS). Steadily (linear) bioaccumulation of MeHg in the fish muscle occurred when the fish were exposed individually to this species during the period. The bioaccumulation of MeHg is diminished when the fish are firstly exposed to SeMet and then to MeHg, hence indicating the MeHg detoxification due to SeMet supplementation.
- Towards a better assessment of the mercury-selenium antagonism in fishPublication . Mendes Ribeiro, Mariana; Zephyr, N.; Silva, José Armando; Damion, M.; Guérin, T.; Castanheira, Isabel; Leufroy, A.; Jitaru, P.The fish were killed by cutting the spinal cord in t 0 t 1 t 2 and t 3 All the data related to the fish growth were recorded similar growth was observed for all exposure conditions. The levels of Hg T and Se T in the fish diet were also measured by ICP MS. Hg T in control and MeHg spiked diets were 0.05 ±0.002 and 0.24 ±0.01 mg/kg, respectively, whereas Se T were 0.95 ±0.02 mg/kg and 5.41 ±0.36 mg/kg in the control and the spiked diets. Se saturation ( p = 0.30) occurs after two months of fish be exposed throught diet to SeMet solely. Quasilinear (R 2 0.99) bioaccumulation of Hg in the fish exposed individualy to MeHg during 3 months. Threshold (p = 0.30) in total Hg level is reached in fish exposed simultaneously to MeHg and SeMet. ↓ of Hg burden 18%) after two months of fish exposure to SeMet and no MeHg. Possible Hg detoxification due to Se supplementation.