Environmental monitoring by gene expression biomarkers in Barbus graellsii: Laboratory and field studies

11 pages, 3 figures, 2 tables.-- PMID: 17217992 [PubMed].-- Printed version published Apr 2007.Barbel (Barbus graellsii) is a freshwater fish used as a sentinel species in environmental monitoring programmes and ecotoxicological studies in northern Spain, particularly in the Ebro River basin, the largest freshwater resource in Spain. We developed specific primers for the quantification of CYP1A and metallothionein (MT)-1 and -2 gene expression by QRT-PCR in barbel in order to assess their suitability in biological effect monitoring of dioxin-like compounds and metals. All three genes responded as expected in laboratory tests, using model inducers. Hepatic CYP1A mRNA levels showed a twofold induction in fish injected intraperitoneally with b-naphthoflavone, whereas MT-1 and MT-2 gene expression was strongly induced by cadmium (15- and 13-fold, respectively) and mercury (five- and eightfold). Barbel populations from different sites on the Ebro River basin showed a good correlation between the historical records of organochlorine pollution, CYP1A expression levels and EROD activity. Nevertheless, although metallothionein protein levels in the liver of wild fish correlated with hepatic levels of mercury, MT-1 and MT-2 gene expression did not correlate with the mercury content or with the concentration of metals in sediments from the sites inhabited by the fish. These results demonstrate the utility of barbel CYP1AmRNA expression, but not that of MT-1 or MT-2, as a biomarker in field studies. The tools and protocols developed here are likely to apply to other species of the genus Barbus, with some 700 species distributed throughout most of the Old World.This work has been supported by the European Union, and reflects only the author’s views and the European Community is not liable for any use that maybe made of the information contained there in "Integrate modelling of the river–sediment–soil–groundwater system; advanced tools for the management of catchment areas and river basins in the context of global change" (AQUATERRA, GOCE-CT-2004-505428). The Spanish Ministry of Education and Science [CTM2005-25168-E/CGL-2004-03514/HD, BIO2005-00840] is thanked for complementary financial support. D. Raldúa acknowledges the "Ramón y Cajal" contract from the Spanish MEC.Peer reviewe