Accumulation of Cadmium and Antioxidant and Hormonal Responses in the Indian Major Carp <Emphasis Type="Italic">Cirrhinus mrigala</Emphasis> During Acute and Sublethal Exposure

Acute (24 h) and sublethal (35 days) effects of cadmium chloride (CdCl₂) were examined in Cirrhinus mrigala using various endpoints (accumulation pattern, thyroid hormones (THs), and antioxidants). The mean concentrations of CdCl₂ for 24 and 96 h were found to be 35.974 and 22.387 mg L^?l, respectively. LC50 concentration of CdCl₂ for 24 h (35.97 mg L^?l) was used for the acute study. For the sublethal studies, fish were exposed to 3.59 mg L^?1 (Treatment I) and 7.19 mg L^?1 (Treatment II) corresponding to 1/10th and 1/5th of 24 h LC50 of the CdCl₂. During acute exposure, higher accumulation of CdCl₂ was noticed in the gill, liver, and kidney of C. mrigala, which is found in the order gill > liver > kidney tissues. Similarly, in sublethal treatments (Treatment I and II), a concentration and time-dependent increase of CdCl₂ accumulation was noticed in the order of gill > liver > kidney. GSH, GST, and GPx activities were found to be relatively lower from the treated groups in both acute and sublethal treatments. However, LPO activity was significantly increased in CdCl₂-treated fish C. mrigala. Further, plasma T₃ reduction was more pronounced than T₄ in acute study. During sublethal treatments, both T₄ and T₃ levels showed a continuous decrease as the exposure period extended. All the values in this study were statically significant (P < 0.01 and P < 0.05).