Acute Nitrite Exposure Induces Dysfunction and Oxidative Damage in Grass Carp Isolated Hemocytes

Abstract

To evaluate the effects of nitrite on the oxidative damage of blood cells of Grass Carp Ctenopharyngodon idella, the isolated hemocytes were exposed to nitrite (0, 1, 10, or 100 mg/L) for up to 24 h. Hemoglobin (Hb) and methemoglobin (MetHb) concentrations, reactive oxygen species (ROS) and malondialdehyde (MDA) levels, mitochondrial membrane potential (∆Ψm), and antioxidant enzyme activity were assayed to assess hematological parameters and the antioxidant defense mechanism. Results showed a remarkable decrease in Hb concentration with increasing nitrite concentration after a 24‐h exposure, while the MetHb concentration increased significantly in nitrite exposure groups. The levels of ROS, ∆Ψm, and MDA increased to varying degrees with increases in nitrite exposure concentration and time. The total antioxidant capacity, catalase (CAT) activity, glutathione peroxidase (GPx) activity, and glutathione content showed a trend of rising initially and then decreasing with prolonged exposure time. Superoxide dismutase (SOD) activity was higher in the 1‐mg/L nitrite exposure group and lower in the 100‐mg/L group than in the control. The relative messenger RNA expression ratios of cat, sod1, and gpx were up‐regulated significantly in the 1‐ and 10‐mg/L groups and then declined in the 100‐mg/L group. Therefore, it can be concluded that nitrite exposure activates the antioxidant defense mechanism of Grass Carp hemocytes and that the balance of oxidant–antioxidant homeostasis will be undermined by higher nitrite doses or longer exposure periods.

Analysis of Acute Nitrite Exposure on Physiological Stress Response, Oxidative Stress, Gill Tissue Morphology and Immune Response of Large Yellow Croaker (Larimichthys crocea)

“…Therefore, fish are vulnerable to aberrant environmental stress factors and display variations in physiologic parameters and stress response [ 2 ]. Nitrite is an intermediate toxic product produced by bacteria in the process of ammonia nitrification to nitrate and denitrification [ 3 ]. In aquaculture environments, nitrite can easily reach toxic levels and seriously affect the normal growth and health status of aquatic animals [ 4 ].…”

“…Kim et al found that nitrite exposure induced an increase in SOD activity in the liver and gills, indicating that nitrite exposure increased the production of ROS and affected antioxidant responses [ 9 ]. Zhang et al also reported that nitrite increased the total antioxidant capacity, CAT activity, GSH-Px activity, and glutathione content with prolonged exposure time [ 3 ]. Stress enhancement and the accumulation of oxygen free radicals in the body depress the antioxidant system and directly or indirectly impair the immune viability of the fish.…”