Short-term mercury exposure on Na+/K+-ATPase activity and ionoregulation in gill and brain of an Indian major carp, Cirrhinus mrigala.

Abstract: Recently mercury pollution has been increased considerably in aquatic resources throughout the world and it is a growing global concern. In this study, the 96h LC50 value of waterborne mercuric chloride for Cirrhinus mrigala was found to be 0.34mg/L (with 95% confidence limits). Fingerlings of C. mrigala were exposed to 0.068 and 0.034mg/L of mercuric chloride for 96h to assess the Na⁺/K⁺-ATPase activity and ionoregulation (Na⁺, K⁺ and Cl⁻) in gill and brain. Results showed that Na⁺/K⁺-ATPase activity and ionic levels (Na⁺, K⁺ and Cl⁻) in gill and brain of fish exposed to different concentrations of mercuric chloride were found to be significantly (p <0.05) decreased throughout the study period. Mercury inactivates many enzymes by attaching to sulfur atoms in which the enzyme Na⁺/K⁺-ATPase is highly sensitive to mercury. The inhibition of gill and brain Na⁺/K⁺-ATPase activity might have resulted from the physicochemical alteration of the membrane due to mercury toxicity. Moreover, inhibition of Na⁺/K⁺-ATPase may affect the ion transport and osmoregulatory function by blocking the transport of substances across the membrane by active transport. The present study indicates that the alterations in these parameters can be used in environmental biomonitoring of mercury contamination in aquatic ecosystem. [Copyright &y& Elsevier]