Changes in the physiological indicators and gene expression for grass carp (Ctenopharyngodon idella) in response to alkaline stress

Alkalinity stress is a significant abiotic factor influencing fish growth and productivity. Understanding the mechanisms underlying fish tolerance to saline–alkaline stress is essential for developing highly resistant fish strains and expanding the potential for freshwater aquaculture. This study examined the impact of alkaline stress on the survival rate, digestive enzyme activities, tissue morphology, and gene expression profiles in juvenile grass carp. Acute stress experiments revealed that the LC₅₀ value for juvenile grass carp (31.72 ± 8.88 g) exposed to alkalinity for 96 h was 44.11 mM, indicating relatively high tolerance to alkalinity. Furthermore, NaHCO₃-induced alkaline stress significantly affected digestive enzyme activities and tissue morphology. A tissue-specific transcriptome analysis (gill, liver, and kidney) was conducted at various time points during alkalinity stress exposure, identifying numerous differentially expressed genes and pathways associated with alkaline stress. Notably, several alkali-responsive genes, including serpinh1b, aqp10a, cbr11, scos3b, and mycb, were differentially regulated across the compared groups in PCR Array. The findings provide valuable insights into the mechanisms of alkaline stress tolerance.