Yao Zongli, Guo Wenfei, Lai Qifang, Shi Jianquan, Zhou Kai, Qi Hongfang, Lin Tingting, Li Ziniu, Wang Hui
J Comp Physiol B. 2016 Jan;186(1):83-95. doi: 10.1007/s00360-015-0939-z.
Naked carp (Gymnocypris przewalskii), endemic to the saline-alkaline Lake Qinghai, have the capacity to tolerate combined high salinity and alkalinity, but migrate to spawn in freshwater rivers each year. In this study, the full-length cDNA of the cytosolic carbonic anhydrase c isoform of G. przewalskii (GpCAc) was amplified and sequenced; mRNA levels and enzyme activity of GpCAc and blood chemistry were evaluated to understand the compensatory responses as the naked carp returned to the saline-alkaline lake after spawning. We found that GpCAc had a total length of 1400 bp and encodes a peptide of 260 amino acids. Comparison of the deduced amino acid sequences and phylogenetic analysis showed that GpCAc was a member of the cytosolic carbonic anhydrase II-like c family. Cytosolic-carbonic-anhydrase-c-specific primers were used to analyze the tissue distribution of GpCAc mRNA expression. Expression of GpCAc mRNA was found in brain, gill, liver, kidney, gut, and muscle tissues, but primarily in the gill and posterior kidney; however, none was evident in red blood cells. Transferring fish from river water to lake water resulted in a respiratory alkalosis, osmolality, and ion rise in the blood, as well as significant decreases in the expression and enzyme activity of GpCAc in both the gill and kidney within 96 h. These results indicate that GpCAc may play an important role in the acclimation to both high salinity and carbonate alkalinity. Specifically, G. przewalskii decreases cytosolic carbonic anhydrase c expression to compensate for a respiratory alkalosis and to aid in osmoregulation during the transition from river to saline-alkaline lake.
裸鲤（青海湖裸鲤）是盐碱化的青海湖特有的鱼类，具有耐受高盐度和高碱度的能力，但每年都会洄游到淡水河流中产卵。在本研究中，对青海湖裸鲤胞质碳酸酐酶c亚型（GpCAc）的全长cDNA进行了扩增和测序；评估了GpCAc的mRNA水平、酶活性及血液化学成分，以了解裸鲤产卵后返回盐碱湖时的代偿反应。我们发现GpCAc全长1400 bp，编码一个由260个氨基酸组成的肽段。推导的氨基酸序列比较和系统发育分析表明，GpCAc是胞质碳酸酐酶II样c家族的成员。使用胞质碳酸酐酶c特异性引物分析GpCAc mRNA表达的组织分布。发现GpCAc mRNA在脑、鳃、肝、肾、肠和肌肉组织中均有表达，但主要在鳃和后肾中；然而，在红细胞中未检测到明显表达。将鱼从河水转移到湖水中会导致血液中出现呼吸性碱中毒、渗透压和离子升高，同时在96小时内鳃和肾中GpCAc的表达和酶活性均显著降低。这些结果表明，GpCAc可能在适应高盐度和碳酸盐碱度方面发挥重要作用。具体而言，青海湖裸鲤会降低胞质碳酸酐酶c的表达，以补偿呼吸性碱中毒，并在从河流向盐碱湖过渡期间协助渗透压调节。
