Impact of abrupt salinity changes on activitiy of metabolic enzymes, antioxidant enzymes and cortisol content in serum and liver of <italic>Lateolabrax maculatus</italic>

Abstract

<italic>Lateolabrax maculatus</italic> is an important economic fish species in China. It is a eurysaline species and can survive and grow in water environment with varieties of salinity. It is of practical significance to study the tolerance and adaptability of <italic>L</italic>. <italic>maculatus</italic>, because it usually suffers from sudden increase or decrease of salinity in aquaculture environment. This work investigated the effects of abrupt salinity changes on the activitiy of metabolic enzymes and antioxidant enzymes and cortisol content in liver of <italic>L</italic>. <italic>maculatus</italic> by simulating salinity changes of water for its breeding. The salinity was reduced from 18 to 0 and remained for 7 d, and then increased to 33 sharply after acclimation and remained for 7 d. Correspondingly, in the other treatment, the salinity increased from 18 to 33, and then decreased to 0 sharply after acclimation and remained for 7 d. Samples were taken on 0, 0.5, 1, 3,7 d after the start of the experiment, respectively. The activitiy of alkaline phosphatase, acid phosphatase, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase, superoxide dismutase, catalase, glutathione peroxidase in serum and liver of <italic>L</italic>.<italic>maculatus</italic> was tested, and cortisol (COR) content in serum was monitored as well. Results showed that the abrupt salinity changes would have impact on activitiy of metabolic enzymes and antioxidant enzymes, and COR content of <italic>L</italic>.<italic>maculatus</italic>. The activitiy of enzymes and COR content showed a trend of increasing firstly and then declining with time prolonging under most situations of abrupt salinity changes. These results showed that <italic>L</italic>.<italic>maculatus</italic> had a stress reaction during the abrupt changing of salinity, and could adapt to the change within 3-7 days, which indicated that <italic>L</italic>.<italic>maculatus</italic> had a substantial tolerance and adaptability to the abrupt changes in salinity. The changes of morphological characteristics, metabolic enzyme activity, antioxidant enzyme activity and COR content showed that <italic>L</italic>.<italic>maculatus</italic> could more rapidly adapt to sudden drop in salinity and was more adaptable to low-salinity environment.