Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Applicability of novel test methods for in field monitoring

The induction of vitellogenin (Vtg) in fish is an estrogen dependent process, which normally active in maturing females, can also be activated, in immature females and males when exposed to estrogens and their mimics. Paralleling what happens in plasma, Vtg can be detected in skin mucus and enhanced by estrogens. This observation has supported the proposal of using skin mucus Vtg as a non destructive biomarker of exposure to estrogens.

The necessary premise to a routine application of this biomarker was the development of a simple assay, which can rapidly detect Vtg in the mucus of large numbers of fish. The method of choice was immunological and the dipstick assay developed for carp Vtg was applied both to fish exposed in laboratory and to the many individuals captured in seven areas of the River Po basin, with different levels of contamination. The point of strength of this tool is that it is non destructive and harmless to fish. Moreover, although still a prototype, the dipstick resulted to be very rapid to perform and of easy applicability, particularly in field. Also the evaluation of results is quite simple, since a coloured test line appears when Vtg is present in the sample.

Comparison of Vtg levels in plasma and mucus of the same fish using a quantitative sandwich ELISA previously established (Nilsen et al., 2004) indicated a positive correlation in almost all groups of carp investigated. Interestingly, in some of the fish groups, no correlation or a negative correlation was observed. This was most pronounced in samples from the field and from the tamoxifen (TAM) exposure groups. The lack of correlation between plasma and mucus Vtg indicates different turnover of Vtg in these sample types. In the field sampling, there was a general lack of Vtg in the mucus, although varying levels of Vtg was found in plasma. It is possible that fish of various age groups show different Vtg kinetics, and that fish displaying correlations that were more consistent and significant, like the EE2, flutamide, methyldihydrotestosterone, and mixed exposure, were from more homogeneous populations.

Therefore, care should be taken when using the non-invasive strategy in the field. Apparently, exposure to antiestrogens may disturb the Vtg turnover such that mucus and plasma Vtg are no longer in equilibrium. Possibly, a blood sample should be taken, which still could be analysed by the LFIA in a few minutes in the field. From larger specimens, blood sampling could also be a non-destructive strategy. Further studies should be performed to elucidate this.

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