Biomarkers involved in energy metabolism and oxidative stress response in the liver of Goodea gracilis Hubbs and Turner, 1939 exposed to the microcystin-producing Microcystis aeruginosa LB85 strain.

Goodea gracilis is an endemic fish that only habitats in some water bodies of Central Mexico that are contaminated with cyanobacteria-producing microcystins (MC); however, a lack of information on this topic prevails. With the aim to generate the first approximation about the physiological changes elicited by cyanobacterium that produce MC congeners in this fish species, specimens born in the laboratory was exposed for 96 h to cell densities of 572.5, 1145, 2290, 4580, and 9160 × 10(6) cells of Microcystis aeruginosa strain LB85/L, and a set of novel endpoint related to hepatic gluconeogenesis (ADH/LDH) and pro-oxidant forces O2., H2 O2 ) in addition to biomarkers of oxidative damage and antioxidant response was evaluated in the liver. Results suggest that high inhibition of protein serine/threonine phosphatase (PP) may trigger many metabolic processes, such as those related to hepatic gluconeogenesis (ADH/LDH) and pro-oxidant O2⋅, H2 O2 , TBARS, ROOH, RC=O) as well as antioxidant (SOD, CAT, GPx) response to oxidative stress. Particularly, we observed that inhibition of LDH and PP, and H2 O2 increase and TBARS production were the key damages induced by high densities of M. aeruginosa. However, changes between aerobic and anaerobic metabolism related with ROS metabolism and ADH/LDH balance are apparently an acclimation of this fish species to exposure to cyanobacteria or their MCs. Fish species living in environments potentially contaminated with cyanobacteria or their MCs possess mechanisms of acclimation that allow them to offset the damage induced, even in the case of fish that have never been exposed to MCs.

Pro-oxidant and antioxidant responses in the liver and kidney of wild Goodea gracilis and their relation with halomethanes bioactivation.

In mammals, it has been shown that halomethanes (HM) are bioactivated by enzymes such as CYP 2E1 and the theta isoform of GST to produce reactive metabolites. However, in fish, little information is available, although HM can form autochthonously in aquatic environments. This study assessed the effect of HM in dusky splitfin (Goodea gracilis) from three lakes of the Valley of Mexico by analysing specific HM biomarkers as well as a broad range of biomarkers. The concentration of HM was a function of its half-life (higher in deep waters), while its precursors and solar radiation are secondary factors that determine its concentration. The kidney showed higher basal metabolism than the liver, probably because of its function as a haematopoietic and filtration organ. Using integrated biological response version 2 (IBRv2), it was found that the hepatic and renal O2· content is a pro-oxidant force capable of inducing oxidative stress (ROOH, TBARS and RC=O). Early damage was found to be dependent on low concentrations of HM in Major Lake, whereas late damage was observed in fish exposed to higher concentrations of HM in Zumpango Lake and Ancient Lake. The activities of enzymes involved in antioxidant defence seemed to be inefficient. The quantitative assessment of biomarkers (ANOVA) and the estimate of parameter A obtained from IBRv2 provided different information. However, the data support the greater predictive power of IBRv2, but it requires a series of interrelated biomarkers to infer these possibilities. G. gracilis presents marked patterns of adaptation, which are dependant on the HM concentrations in environmental mixtures, although the response is complex and many toxicants could induce similar responses.