Distribution of mercury species in different tissues and trophic levels of commonly consumed fish species from the south Bay of Biscay (France).

Mercury (Hg) is a contaminant of global concern in marine ecosystems, notably due to its ability to accumulate and concentrate in food webs. Concentrations of total mercury (THg), methylmercury (MeHg) and inorganic mercury (IHg) were assessed and compared in different tissues (liver, muscle, and gonads) of three common fish species (hake Merluccius merluccius, red mullet Mullus surmuletus, and sole Solea solea) from the continental shelf from the southern part of the Bay of Biscay. Several studies investigated Hg concentration in fish muscle, but few assessed concentrations in other organs, despite the importance of such data to understand contaminant organotropism and metabolization. Results showed that trophic position and feeding habitat are required to understand the variability of Hg concentration in muscle between fish species. In addition, high MeHg/THg ratio in muscle could be explained by the predatory behavior of the studied fish species and the biomagnification of this Hg species within the food web, MeHg. Despite differences between species, Hg concentration was always higher in muscle (from 118 ± 64 to 338 ± 101 ng g-1 w.w.) and liver (from 122 ± 108 to 271 ± 95 ng g-1 w.w.). These results can be related to physiological processes especially the MeHg detoxification strategies.

A simple and fast LC-MS/MS method with a very high sensitivity for the measurement of raltitrexed in human plasma.

Raltitrexed is a thymidylate synthase inhibitor that can be administered safely to patients with cardiovascular disease or dihydropyrimidine dehydrogenase deficiency, as opposed to 5FU. The recommended dose of 3mg/m2 every 3 weeks often leads to toxicity. Interestingly, the 2mg/m2 every 2 weeks dose appears to be less toxic. A pharmacokinetic trial was then performed by our team to investigate such phenomenon. However, there are currently, two main methods for RTX measurement described in the literature: a radioimmunoassay (RIA) and chromatographic-based methods with either UV or mass spectrometry detections. The RIA methods: display a low limit of quantification (below 1µg/L), but also a low extent of linearity for the calibration curve. The chromatographic-based methods: include high level of calibrators, but have poor sensitivity (>2µg/mL). If a high sensitivity is essential to satisfactorily describe the elimination of RTX, high concentrations in the calibration curve are also needed to avoid bias linked to the dilutions of the samples. A new LC-MS/MS method was then developed that allows to simultaneously measure very low (0.1µg/L) and very high (3000µg/L) concentrations in the same run. Moreover, the extraction steps are very simple and fast with mainly a precipitation and a filtration steps. This method was validated following the EMA recommendations. In view of the extent of the calibration curve, the carry-over effect was more deeply investigated. With this method, it was possible to measure RTX in samples taken 3 weeks after the administration. Taken together, this method allows to simply and quickly measure RTX in plasma of patients.