Single and combined effects of ammonia and nitrite on common carp, Cyprinus carpio: Toxicity, hematological parameters, antioxidant defenses, acetylcholinesterase, and acid phosphatase activities

Ammonia and nitrite are two of the most toxic substances for ecosystems and aquatic organisms. The present study aimed to investigate the single and combined effects of ammonia and nitrite on hematological parameters, antioxidant defenses, acetylcholinesterase, and acid phosphatase activities in common carp. First, LC₅₀–96 h of ammonia and nitrite in common carp were determined. Second, fish were exposed to four experimental groups contained control, 30% LC₅₀–96 h ammonia, 30% LC₅₀–96 h nitrite, and 30% LC₅₀–96 h ammonia+30% LC₅₀–96 h nitrite for 96 h. WBCs were significantly elevated in fish exposed to 30% LC50–96 h ammonia and nitrite in all treated groups compared to the control group. RBCs and hemoglobin amount in all exposed groups were significantly decreased compared to the control after 96 h of exposer. Moreover, a significant decrease was observed in the hematocrit level in ammonia and ammonia+nitrite groups compared to the control group. Furthermore, exposure to 30% LC50–96 h ammonia and nitrite resulted in a significant alteration in blood indices (MCV, MCH, and MCHC) after 96 h. The serum CAT activity was significantly higher in the exposed groups than the control group after 96 h. The serum MDA activity was considerably higher in fish exposed to nitrite compared to the control group. Levels of serum total antioxidant were strongly lower in all exposed groups after 96 h. Moreover, the serum AChE activity reduced considerably in all groups compared with the control group. Serum ACP levels were significantly elevated in all exposed groups compared to the control group. Overall, our findings suggest that the single and combined presence of nitrite and ammonia in water can cause adverse effects in some blood indices, serum AChE, ACP activities, and antioxidant defenses in common carp.