| This study examined the effects of salinity stress on the antioxidant system of the liver, kidney, and gill and the serum cortisol levels of Luciobarbus capito. Four NaCl salinity groups (3, 6, 9, and 12 g/L) and a freshwater control group were set up in this experiment. Further, we detected the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), glutathione peroxidase (GSH-Px), and the content of malondialdehyde (MDA) in the liver, kidney, and gill, as well as the serum cortisol level at seven salinity exposure time points (3 h, 6 h, 12 h, 24 h, 48 h, 96 h, and 7 d). The results indicated that under salinity stress, the antioxidant enzyme activity, MDA content in the liver, kidney, and gill, and serum cortisol levels were increased and then decreased as the stress exposure time increased, after which they tended to be stable. They reached the maximum value within 24 h after exposure of L. capito to salinity and reduced within 48 h and stabilized within 96 h~7 d. Antioxidant enzyme activities, MDA content in the liver, kidney, and gill; and serum cortisol levels were proportional to salinity. Further, ACP, AKP activity, and MDA content were higher in the kidney than in the liver and gill under salinity stress. ACP activity was approximately 1.27~1.96 U/g prot in the liver, 1.42~2.15 U/g prot in the kidney, and 0.98~1.96 U/g prot in the gill; AKP activity in these three tissues was approximately 0.31~0.86, 1.01~1.87, and 0.13~0.84 king unit/g prot, respectively, and MDA content was 17.02~55.98 nmol/mg prot, 13.05~57.27 nmol/mg prot, and 8.33~53.93 nmol/mg prot, respectively. However, GSH-Px activity in the three tissues was 44.41~114.77, 16.52~67.59, and 9.07~48.00 active unit, respectively, indicating that it was significantly higher in the liver than in the kidney and gill. In addition, serum cortisol level was 197.00~355.50 ng/L under salinity stress. Overall, L. capito can become normal through self-regulation under 12 g/L salinity, indicating that they have strong adaptability to saline environment. |
