Ammonia is a major pollutant in aquatic environments and poses a considerable threat to the survival of fish. In this study, we investigated the toxic effects of ammonia on the hematological and biochemical parameters, oxidative stress, and immune responses in Takifugu rubripes. Juvenile T. rubripes (average weight 246.17 ± 3.54 g) were exposed to different concentrations of ammonia (0, 5, 50, 100, and 150 mg/L) for 96 h. The results showed that the hematological parameters (hemoglobin, hematocrit, red blood cell, and white blood cell count) were significantly reduced in response to ammonia exposure. Of the plasma components, such as serum total protein, albumin, glucose, glutamic-oxalacetic transaminase, and glutamic-pyruvic transaminase, were significantly altered in response to ammonia exposure. Additionally, the levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GPx) were increased after exposure to low concentration ammonia exposure. However, when fish were exposed to a high concentration of ammonia, these parameters showed the opposite trend, suggesting that an increase in antioxidant enzymes during the early stages of ammonia exposure may contribute to the removal of the induced reactive oxygen species (ROS) and protect the cells from oxidative damage. However, as the ammonia concentration and exposure time increased, the overproduction of ROS accelerated the depletion of antioxidant enzymes. Ammonia exposure significantly increased the expression of heat shock proteins (HSP70 and HSP90). Ammonia poisoning elevated gene expressions of TLR-3, TNF-α, IL-6, IL-12, and IL-1β in the gills, causing an inflammatory response. Our findings provide new insights into the mechanisms involved in ammonia-induced aquatic toxicology in marine fish, which may aid in their captive management.
Keywords: Ammonia stress; Hematological parameters; Inflammatory cytokines; Oxidative stress; Takifugu rubripes.
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