Transcription Alteration of Immunologic Parameters and Histopathological Damage in Common Carp (Cyprinus carpio L.) Caused by Paraquat

The toxic effects of paraquat (PQ) on the transcription of immunoglobulin M (IgM), complement C3 (C3), and lysozyme (LYZ) and the histopathological alteration of the liver, kidney, and spleen of common carp were evaluated by subacute exposure to 1.596 or 3.192 mg/L of PQ for 7 days. The results demonstrated that PQ exposure altered the transcription of IgM, C3, and LYZ. For example, IgM and C3 expression was generally downregulated, but LYZ was either down- or upregulated, suggesting that PQ may disturb the function of the fish immune system. The results of the histopathological examination revealed that the liver, kidney, and spleen of PQ-treated fish were injured. These injuries included cellular swelling, intracytoplasmic vacuolization, nucleus distortion, and pycnosis in the liver and spleen, and vacuolization of the renal parenchyma and intumescence of the renal tubule in the kidney. This finding indicates that PQ causes toxicity in common carp.