Study on the mechanism of alkaline stress on the immune, antioxidant and osmotic regulation of largemouth bass (Micropterus salmoides)

Alkaline inhibited immunity via immune markers and pathways in largemouth bass. • Alkaline impaired osmoregulation via serum ions and gut osmotic genes in largemouth bass. • Alkaline disrupted antioxidant balance and induced tissue injury in largemouth bass. The purpose of this study was to evaluate the harm of high alkalinity to largemouth bass through physiological and biochemical and transcriptome analysis, and to elucidate its potential molecular mechanism, so as to provide theoretical basis for the sustainable development of alkaline aquaculture. The largemouth bass were divided into normal control group (NC) and alkaline stress group (AS). Freshwater was used for the NC group. Na₂CO₃ and NaHCO₃ were added to the water to reach an additional alkalinity of 6 mmol/L for the AS group. Under alkaline stress, a total of 2014 differentially expressed genes were identified, of which 428 genes were up-regulated and 1586 genes were down-regulated; some serum immune-related indicators decreased significantly, and the differential genes in the immune-related pathways (Calcium signaling pathway, Toll-like receptor signaling pathway and Focal adhesion) in the intestinal tissue were down-regulated as a whole; at the same time, intestinal antioxidant-related indicators (CAT, GSH, MDA, T-AOC) were increased significantly, GSH-Px activity was decreased significantly, and genes in antioxidant-related pathways (Peroxisome, Glutathione metabolism) were also up-regulated as a whole. In addition, the concentration of Na + in serum was decreased significantly, the concentration of K + and Cl − were increased significantly, and the serum osmotic pressure showed a downward trend. Alkaline stress also reduced the expression of osmotic pressure regulatory genes ( cldn15b , ca12 , abcc9 , entpd1 ) in the intestine significantly, and enhanced the expression of slc13a1 . In conclusion, alkaline stress could significantly inhibit the immune function and osmotic pressure regulation ability of largemouth bass, disrupt the balance of its antioxidant system, and cause various damages to the health of the body. Download: Download high-res image (210KB) Download: Download full-size image