Effects of cadmium on the female reproductive axis of a Neotropical fish

Metals are one of the contaminants released from the increase of anthropic activities. They can be classified as endocrine disruptors once they can affect the reproductive parameters of different organisms. The aim of the study was to evaluate the potential effects of cadmium on regulatory reproduction axis (Hypothalamic-Pituitary-Gonadal-Liver, the HPGL axis) in females of Rhamdia quelen exposed to nominal concentrations of 0.1; 1; 10 and 100 μg.L^-1 of cadmium. After 15 days, tissues were collected for hormonal quantification, brain aromatase (cyp19a1b), hepatic vitellogenin (vtg) gene expression, and biomarkers analysis. Cadmium was quantified in water, gonad and liver samples. The plasma levels of estradiol, testosterone and gonad and hepatosomatic indexes did not changed after Cd exposure. The cyp19a1b was not different among the groups. Cadmium was detected at higher concentrations in the liver compared to the gonads. No genotoxicity was observed, only erythrocytes nuclear alterations. Metallothionein was reduced at 10 μg.L^-1 in the liver and 10 and 100 μg.L^-1 in the gonad. Hepatic superoxide dismutase activity increased and this can lead to a hydrogen peroxide increase, one of reactive oxygen species. This increase without a compensation of other enzymes of the antioxidant system can lead to lipoperoxidation, as occurred at 100 μg.L^-1. Hepatic vitellogenin gene expression increased as well as the injury index at 0,1 and 100 μg.L^-1. The tested cadmium concentrations have been found in the freshwater ecosystems and can affect the female reproductive regulation axis HPGL of the Neotropical species R. quelen.