Lead is a persistent environmental pollutant with pronounced toxicological effects on aquatic organisms, particularly fishes that serve as vital components of the food chain. The present investigation evaluates the impact of lead nitrate on the activities of two key enzymes that is Blood Alkaline Phosphatase (BAPA) and Macrophage Acid Phosphatase Activity (MAPA)—in the freshwater teleost Channa punctatus. Fish were exposed to varying concentrations of lead nitrate under sub-acute conditions for 7 days and to a chronic dose of 15 ppm for up to 105 days. Enzyme activities were es-timated using standard biochemical assays, and blood lead accumulation was quantified by atomic absorption spectro-photometry. Statistical analyses included one-way ANOVA and Pearson’s correlation coefficient to determine dose- and time-dependent effects. Results revealed a transient elevation in BAPA and MAPA activities during short-term subacute exposure, suggesting an adaptive or stress-induced enzymatic response. In contrast, prolonged chronic exposure resulted in significant inhibition of both enzymes, accompanied by high correlations between blood lead levels and enzyme sup-pression. The inhibition of MAPA indicates compromised macrophage function and impaired cellular immunity, while reduced BAPA activity reflects disturbances in membrane transport and metabolic regulation. These findings demonstrate that chronic lead exposure exerts pronounced immunotoxin and biochemical stress in Channa punctatus. The study underscores the ecological risks of lead contamination in aquatic ecosystems and highlights phosphatase enzymes as sensitive biomarkers of lead-induced toxicity.

Lead Nitrate, Channa punctatus, Blood Alkaline Phosphatase, Macrophage Acid Phosphatase, Immunotoxicity, Thiol Group