盐碱胁迫对尼罗罗非鱼鳃Na^+/HCO_3^-共转运子、碳酸酐酶基因表达的影响

Effects of salinity and alkalinity on m RNA expression of Na^+/HCO_3^- cotransporter and carbonic anhydrase genes from Oreochromis niloticus

为了探讨盐碱胁迫条件下鱼类渗透生理调节机制,以尼罗罗非鱼(Oreochromis niloticus)为实验材料,PCR扩增得到了Na^(+)/3HCO^(-)共转运子(NBCe1)基因c DNA部分序列,比较了单盐(盐度10、盐度15)、单碱(1.5 g/L、3 g/L Na HCO3)、盐碱混合(盐度10,碱度1.5 g/L;盐度15,碱度3 g/L)胁迫后不同时间(0 h、6 h、12 h、24 h、48 h、72 h、96 h)血清渗透压、离子浓度(Na^(+)、K^(+)、Cl–、Ca2^(+))以及鳃碳酸酐酶(CA)活性、CA与NBCe1基因m RNA表达变化。结果显示,不同胁迫条件下,血清渗透压、离子浓度、鳃组织CA酶活、CA与NBCe1基因m RNA表达变化均与胁迫强度呈正相关。随时间推移,血清渗透压、离子浓度呈现先上升后下降的变化趋势,单盐、盐碱混合组血清渗透压值较单碱组高。单盐、单碱、盐碱混合组中,NBCe1基因m RNA在鳃中均呈略微上调,但不显著(P>0.05)。单碱组和盐碱混合组鳃CA活性较单盐组高,低盐碱胁迫(盐度10,碱度1.5 g/L)下CA活性较晚达最高值;不同胁迫条件下,CA基因m RNA表达均表现上调,单碱、盐碱混合组更为显著(P<0.05),推测CA较NBCe1对体内3HCO^(-)转运作用更为显著。研究结果为尼罗罗非鱼盐碱适应生理调节提供了基础资料。

To understand fish osmotic adjustment mechanisms in saline and alkaline water, the partial c DNA sequence was obtained from gills of Oreochromis niloticus. Physiological changes in serum osmolality, ion concentration（Na^＋, K^＋, Cl^– and Ca2^＋）, and gill carbonic anhydrase（CA） activities were determined, and CA and NBCe1 m RNA gene expressions under saline（10 g/L, 15 g/L Na Cl）, alkaline（1.5 g/L and 3 g/L Na HCO3）, and saline-alkaline（salinity 10, 15 g/L Na Cl; salinity 1.5, 3 g/L Na HCO3） conditions at different times（0 h, 6 h, 12 h, 24 h, 48 h, 72 h and 96 h） were compared. The results showed that serum osmolality, ion concentration, gill CA activity, CA and NBCe1 m RNA gene expression correlated positively with the strength of saline, alkaline and saline-alkaline stress. Over time, serum osmolality and ion concentration trends increased and then decreased. Osmotic pressure insaline and saline-alkaline water was higher than that in alkaline water. Gill CA activity in alkaline and saline-alkaline water was higher than that in saline water. Under low concentrations of stressors, CA activity reached its highest level at a later time. Slightly higher NBCe1 gene m RNA expression was detected in gills under high concentrations of stressors（P〈0.05）. Gill CA m RNA expression in saline, alkaline and saline-alkaline water was increased, but the increase was more evident in alkaline and saline-alkaline water（P〈0.05）. The results showed that CA and NBCe1 in Nile tilapia are involved in salinity and alkalinity regulation under osmotic stress. The results provide a basic understanding of the physiological regulation during salinity-alkalinity adaptation.