NaCl regulates goldfish growth and survival at three food supply levels under hypoxia

Abstract

Abstract NaCl has beneficial effects in preventing fish disease. However, the effects of NaCl in regulating fish growth and survival at different food supply levels under hypoxic conditions are unknown. Herein, the effects of NaCl on body weight, survival rate (SR), H2O2 content, lipid peroxidation, protein carbonylation, antioxidant (superoxide dismutase [SOD], catalase [CAT], and glutathione peroxidase [GPX]) enzyme activities, and the glutathione (GSH) content were investigated in goldfish (Carassius auratus) livers at three food supply levels (50, 200, and 400 mg day−1 fish−1) under hypoxic conditions. The highest and lowest SRs were detected in the 200 and 400 mg food groups, respectively. Interestingly, 50 mM NaCl markedly elevated survival, but not the body weight of goldfish. Enhanced H2O2 content; SOD, CAT, and GPX activities; GSH content; and reduced lipid peroxidation and protein carbonylation were detected in goldfish livers after NaCl treatment compared with those in the control. However, these effects of NaCl were dramatically attenuated by 50 µM hydroxychloroquine, an inhibitor of autophagy. This showed that nutrition stress reduced goldfish survival, which could be improved by NaCl via regulation of the antioxidant system and autophagy under hypoxic conditions.