草鱼在不同梯度碳酸盐碱度下的生理响应
摘要
To comprehensively assess the alkali tolerance of grass carp “Husu No.1”, this study examined and analyzed the significant physiological response parameters and related gene expressions in gills of grass carp under varying NaHCO<sub>3</sub> alkalinity gradients: low (10 mmol/L, AW-10), medium (30 mmol/L, AW-30), and high (50 mmol/L, AW-50) over a 7-day period. The findings revealed that in terms of ammonia nitrogen metabolism, as alkalinity increased, the content of blood ammonia exhibited an ascending trend, with the AW-50 group having the highest content. However, there was no significant difference (<italic>P</italic>>0.05) between the low and medium alkalinity groups and the freshwater control group. The content of serum urea nitrogen was lower than that of the freshwater control group. The activity of glutamate dehydrogenase (GDH) and the expressions of <italic>rhbg</italic>, <italic>rhcga</italic>, and <italic>glud1a</italic> in the gills of the medium and high alkalinity groups were upregulated, suggesting that grass carp might carry out ammonia detoxification by enhancing the high expression of ammonia transport genes in the gills and activating the GDH pathway, thereby stabilizing the stability of blood ammonia at medium and low alkalinity. Regarding the immune response, although the numbers of three types of immune cells (white blood cells, lymphocytes, and neutrophils) in different alkalinity groups did not significantly differ from those in the freshwater control group, the numbers of these three immune cells showed an increasing trend with the increase in alkalinity, with the AW-50 group showing the greatest increase. The expression of immune-related gene <italic>c3</italic> was significantly elevated across all alkalinity groups, while <italic>il-1β</italic> was significantly increased in the high alkalinity group, <italic>tnf-α</italic> was significantly increased in the middle alkalinity group, and more serious inflammatory reactions occurred in t