Browsing by Author "Leufroy, A."
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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.
- Évaluation du devenir du mercure et du sélénium dans le poisson lors de la cuissonPublication . Mendes Ribeiro, Mariana; Douis, L.; Silva, José Armando; Castanheira, Isabel; Leufroy, A.; Jitaru, P.Les produits de la pêche sont une source importante de nutriments, cependant, ils peuvent accumuler des niveaux substantiels de métaux toxiques, tels que le mercure (Hg). En effet, le poisson représente la principale voie d'exposition des humains au Hg, remettant en cause la consommation régulière d'un tel régime. La majorité des études concernant l'impact toxique du Hg lorsqu'il est ingéré à partir de poisson, a été liée aux niveaux de Hg dans les produits de poisson cru. Cependant, dans la plupart des cas, le poisson est consommé cuit. Plusieurs variables dans les traitements culinaires (température, mode de cuisson, temps, assaisonnement) peuvent influencer la présence de Hg, dans le poisson. De plus, différentes compositions dans la teneur en Se du poisson peuvent également affecter le devenir du Hg pendant les traitements culinaires. Des études antérieures concernant l'influence de différentes procédures de cuisson sur le devenir du Hg, tirent des conclusions contradictoires. Alors que certains d'entre eux observent une concentration réduite de Hg dans le poisson cuit, d'autres signalent son renforcement. Cette étude vise à évaluer l'effet des divers modes de cuisson traditionnels (bouilli, cuisson à la vapeur et grillé) chez différentes espèces de poissons sur la teneur en Hg. De plus, l'influence du Se sur le devenir du Hg pendant la cuisson a également été abordée.
- Simultaneous speciation analysis of Hg and Se in fish by high-performance liquid chromatography and inductively coupled plasma-mass spectrometry following microwave-assisted enzymatic hydrolysisPublication . Ribeiro, M.; Galli, E.; Guérin, T.; Silva, J.A.L.; Castanheira, I.; Leufroy, A.; Jitaru, P.This study reports the development and validation of a new analytical method for simultaneous speciation analysis of Se and Hg in fish muscle. For this purpose, four Se species (selenite/Se(IV), selenate/Se(VI), selenomethionine/SeMet, and selenocysteine/SeCys) and two Hg species (inorganic mercury/iHg and methylmercury/MeHg) were extracted simultaneously by microwave-assisted enzymatic hydrolysis and then separated by HPLC in less than 15 min by using a column with both anion and cation exchange mechanisms and a mobile phase consisting of a mixture of methanol 5% (v/v), 45 mM HNO3, 0.015% 2-mercaptoethanol, and 1.5 mM sodium 3-mercapto-1-propanesulfonate. The separated species of Hg and Se were detected online by inductively coupled plasma-mass spectrometry (ICP-MS). The speciation analysis method was validated by means of the accuracy profile approach by carrying out three series of measurements in duplicate on three different days over a time-span of 3 weeks. The limits of quantification (LOQ) are in the range of 0.010–0.013 mg/kg wet weight (ww) for all selenium species, except for Se(IV) (0.15 mg/kg ww), while the coefficient of variation in terms of intermediate reproducibility (CVR) was < 7%. The LOQ for MeHg was 0.006 mg/kg ww, while the CVR was 3%. The method was successfully applied to the analysis of muscle samples from four different fish species: rainbow trout, tuna, swordfish, and dogfish.
- 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.