Zinc-Induced Histopathological and Enzymatic Alterations in Kidney and Liver of Common Carp Cyprinus carpio var. Communis: A Comprehensive Analysis

In aquatic environments, heavy metals have been a significant threat to aquatic fauna, including fish, and are considered the most potent contaminant in the aquatic environment. The severity of heavy metal contamination and its potential to alter many physiological and biochemical mechanisms of fish metabolism has attracted the world's attention. Aim: The current study was conducted to investigate the impact of Zinc Sulfate (ZnSO₄) exposure on serum enzyme activities and histopathological alterations in the liver and kidney of Cyprinus carpio. The study was conducted in the Research Laboratory of the Department of Zoology, Central University of Kashmir, between October 2021 and May 2022. The experiment was carried out by obtaining 30 healthy individuals of Cyprinus carpio from the manasbal fish farm of both sexes without any prejudice. Length-weigh parameters were recorded. The specimens were transported from the farm to the laboratory in well-oxygenated containers, and the water was changed three times during transportation. These specimens were placed in a glass tank with 60 L of pure dechlorinated tap water after being treated with a 0.05% KMnO4 solution for 2 min. Before starting the experiment, the fish were acclimatized to laboratory settings for 7 days. Materials and Methods: Fish were exposed to sublethal concentrations of ZnSO₄ for 21 days, and levels of Alkaline Phosphatase (ALP), Aspartate Aminotransferase (AST), and Alanine Aminotransferase (ALT) in serum were measured. Histopathological examinations of the liver and kidney were conducted for 21 days to assess tissue damage. Results: Elevated serum enzyme activities in the exposed group indicated liver and kidney damage. Histopathological analysis revealed hepatocyte degradation, blood vessel congestion, hyalinization, vacuolation, and fatty changes in the liver, while kidney sections exhibited glomerular lesions, dilations of Bowman’s capsule, haemorrhage, and tubular disruptions. Conclusion: The alterations in the liver and kidney were attributed to oxidative stress induced by excess Zn2+ ions, leading to lipid peroxidation and inflammatory response and suggesting that ZnSO₄ exposure adversely affects the liver and kidney of Cyprinus carpio, disrupting normal tissue architecture and function.