The effects of acute exposure to cadmium nitrate (CdNO3) on gambusia fish (Gambusia affinis)

The aim of this study was to assess the impact of cadmium nitrat (CdNO₃) in Gambusia affinis on growth and the development of histopathological changes in gill organs and on the activity of some oxidative stress markers during a 96-hours acute toxicity test. Tests were performed on G. affinis. The average initial weight of fish used in the experiment was 3±1.2 g and the average initial total length of fish was 5.21±3.48 mm. The fish were exposed to a range of CdNO₃ concentrations (1 mg/L, environmental concentration, 0.1, 0.01, 0.001 nad 0.0001 mg/L) for 96 hours. Each test on a CdNO₃-treated group was performed in duplicate. There were no significant differences between the specific growth rates of fish from the test groups and from the control group. Histopathological examination revealed no pathological changes in organs of fish exposed to any CdNO₃ concentration. Significantly lower CAT and SOD activity (p<0.05, p<0.01) was found in fish exposed to CdNO₃ concentrations of 1, 0.1 and 0.01 mg/L compared to the control group; the control group was observed. H2O2, GSH and GPx exhibited significantly higher activity (p<0.01) in the 1, 0.1, 0.01 and 0.001 mg/L groups compared to the control group. But none of these differences were significant (p>0.05). No significance differences (p>0.05) between the control group and any experimental group were found with respect to Protease activity. The MDA level was significantly higher (p<0.01) at a concentrations of 1, 0.1, 0.01 and 0.001 mg/L compared to the control, while in the other experimental groups no significant differences compared to the control group (p>0.05) were observed. According to our results, all tested concentrations of CdNO₃, including the environmental concentration, had an inhibit on oxidative stress markers and detoxifying enzymes in exposed fish, but did not affect fish growth or cause the development of histopathological changes in the fish organism.