碱胁迫下罗非鱼鳃氨转运蛋白Rh基因的表达

为研究碱环境下广盐性鱼类氨转运途径,将尼罗罗非鱼同时进行急性碱度胁迫(2、4、6 g/L)和慢性碱度胁迫,检测胁迫后120 h内的血氨浓度与鳃组织中Rhag、Rhbg、Rhcg1和Rhcg2基因mRNA表达变化,并采用免疫组化技术观察鳃组织中Rh蛋白的阳性反应。结果表明,急性碱度胁迫下,血氨浓度在12 h内快速升高到达峰值,4种Rh基因表达量升高,并于24 h到达峰值;慢性碱胁迫组由于碱度不断升高,血氨浓度呈波动状态,4种Rh基因的表达量均维持在较高表达水平,表明几种Rh蛋白均可能参与血氨浓度调节。胁迫24 h,Rhcg1基因的表达量显著高于其他3种基因。免疫组化结果表明,急性与慢性胁迫组中Rhag、Rhbg和Rhcg在鳃组织中均发现阳性反应,且随碱度升高,阳性反应增强。本研究表明,在碱胁迫环境下,尼罗罗非鱼会增强Rh基因与蛋白表达量参与氨转运过程。

Ammonia Transporter Expression of Rh Protein Gen in Gills of Nile Tilapia Oreochromis niloticus under Stress of Alkali

Blood ammonia concentration and mRNA expression of Rhag,Rhbg,Rhcg1 and Rhcg2 genes in gill were analyzed in Nile tilapia Oreochromis niloticus with body weight of some 50 g exposed to acute alkalinity (NaHCO3 ) stress (2,4,and 6 g/L) and chronic alkalinity stress for 120 h,and the positive reaction of Rh glycoprotein in gill was determined by immunohistochemistry. The results showed that blood ammonia levels were found to be increased rapidly to peak at 12 h,and the expression of four kinds of Rh genes was increased,with the peak at 24 h,under acute alkalinity stress. The concentration of blood ammonia was fluctuated,and the expression of the four Rh genes was maintained at a high level due to the increasing alkalinity in the chronic alkali stress group,indicating that the four kinds of Rh proteins were involved in the regulation of blood ammonia concentration. There was significantly higher expression in Rhcg1 gene than that in the other three genes at 24 h. The immunohistochemical results showed that Rhag,Rhbg and Rhcg in the acute and chronic stress groups were found to be positive in the gill,with increase with the elevated alkalinity. The findings indicated that Nile tilapia exposed to alkalinity had increase in the expression of Rh gene and protein involved in the process of ammonia transport.