Abstract:The effects of pH stress on non-specific immune factors and the RNA/DNA ratio of Marsupenaeus japonicus were investigated. It was found that the activity of total nitric oxide synthase (TNOS) in M. japonicus of low pH group (pH 7.2) and high pH group (pH 9.2) reached the maximum at 3h and 12h, respectively. The activity of inducible nitric oxide synthase (INOS) in pH stress groups reached the maximum at 3h, then gradually declined and stabilized at 72h. The activity changes of phenoloxidase (PO) in M. japonicus under both the low and high pH conditions showed that they reached the peak value at 12h, gradually decreased thereafter, and became stable after 72h. Activities of lysozyme, superoxide dismutase, and glutathione peroxidase in M. japonicus decreased gradually under pH stress. The changes of non-specific immune enzymatic activity showed that the immune adaptive activity in M. japonicus exposed to the high pH stress was lower than those exposed to the low pH stress. Moreover, the RNA/DNA ratio in the muscle of M. japonicus under the pH stress conditions was significantly lower than that of the control group, supposedly due to the effects of pH stress on metabolism of M. japonicus.
