Cellular responses of Prochilodus lineatus hepatocytes after cylindrospermopsin exposure.

Cylindrospermopsin is a potent toxicant for eukaryotic cells produced by several cyanobacteria. Recently, primary hepatocyte cultures of Neotropical fish have been established, demonstrating to be a quite efficient in vitro model for cellular toxicology studies. In the current study, a protocol for culture of Prochilodus lineatus hepatocytes was established and utilized to investigate the cellular responses to purified cylindrospermopsin exposure. Hepatocytes were successfully dissociated with dispase, resulting in a cell yield of 6.36 × 10(7)cells g(-1) of liver, viability of 97% and attachment on uncoated culture flasks. For investigation of cylindrospermopsin effects, hepatocytes were dissociated, cultured during 96 h and exposed to three concentrations of the toxin (0.1, 1.0 or 10 µgl(-1)) for 72 h. Cylindrospermopsin exposure significantly decreased cell viability (0.1 and 1 µgl(-1)) and multixenobiotic resistance mechanism, MXR (all exposed groups), but increased reactive oxygen/nitrogen species levels (all exposed groups) and lipid peroxidation (10 µgl(-1)). On the other hand no significant alterations were observed for other biochemical biomarkers as 2GSH/GSSG ratio, protein carbonyl levels and DNA strand breaks or glutathione S-transferase and glucose 6-phosphate dehydrogenase activities. In conclusion, hepatocytes might be made sensitive to cylindrospermopsin, at least in part, due to reduction of xenobiotics and endobiotics efflux capacity by MXR. Additionally, the toxin exposure suggests important issues regarding hepatocytes survival at the lowest cylindrospermopsin concentrations.

Vitellogenesis and other physiological responses induced by 17-beta-estradiol in males of freshwater fish Rhamdia quelen.

This study investigated the effects of different doses of 17-beta-estradiol (E(2)) in Rhamdia quelen. Groups of males exposed to different doses of E(2) (0.1 mg kg(-)(1), 1 mg kg(-)(1) and 10 mg kg(-)(1)) were compared with non-exposed male and female fish groups. Among the considered biomarkers, no significant differences were observed for micronuclei test, reduced glutathione concentration and lipid peroxidation. All E(2)-treated individuals had decreased glutathione S-transferase activity. Increased catalase and superoxide dismutase activities, increased vitellogenin expression and decreased metallothionein concentration were observed in males treated with the highest dose. Liver of all test groups showed necrotic areas, but cytoplasm vacuolization was again found only in the individuals exposed to highest dose. E(2) causes deleterious hepatic effects to R. quelen, and vitellogenin expression, catalase and superoxide dismutase activity and metallothionein concentration represent appropriate biomarkers for studying E(2) effects. Additionally, the response of some biomarkers was similar in males exposed to E(2) and unexposed females, and therefore exposure to endocrine disruptors may cause consequences for fish populations.