大菱鲆胃质子泵(H^+/K^+ ATPase)与消化机能发生的关系

ACID DIGESTION IN TURBOT SCOPHTHALMUS MAXIMUS BASED ON H^+/K^+ ATPase

胃质子泵(H+/K+ATPase)是胃酸分泌的关键酶。本试验采用RACE和PCR方法从大菱鲆的胃组织中提取RNA克隆得到了H+/K+ATPaseα亚基cDNA全长序列。结果表明:大菱鲆H+/K+ATPaseα亚基序列全长3467 bp,开放阅读框为2964 bp,编码988个氨基酸。与GenBank上其它物种比对发现,大菱鲆H+/K+ATPaseα亚基与斑鳜同源性最高,为89%。进化树分析发现,H+/K+ATPase在进化上具有物种特异性。经RT-PCR和荧光定量PCR检测,大菱鲆H+/K+ATPase在胚胎孵化后22d开始表达,晚于大菱鲆胃腺出现的时间(16 d),说明大菱鲆胃腺的发育完成并不代表胃功能的完善。另外,大菱鲆H+/K+ATPase除了在胃中大量表达之外,在食道中的表达量也很高。结合组织学观察,作者认为,大菱鲆H+/K+ATPase在食道中大量表达是因为在发育上食道是胃的前体,因此保留了分泌H+/K+ATPase的能力。同时通过整体原位杂交试验表明:大菱鲆H+/K+ATPase会首先在食道的末端和胃的贲门处表达。本研究为进一步了解海水鱼类的消化机制提供了理论基础。

Gastric proton pump(H+/K+ ATPase) is a key enzyme involved in gastric acid secretion.We isolated a full-length cDNA sequence of α subunit of H+/K+ ATPase from gastric tissue of turbot Scophthalmus maximus through RT-PCR and RACE(Rapid amplification of cDNA ends).Results indicate that H+/K+ ATPase cDNA was 3467 bp from which 988 amino acids were deduced.The nucleotied sequence of α subunit of H+/K+ ATPase shared high homology with Siniperca chautsi(89%).Phylogenetic analysis showed that H+/K+ ATPase was species-specific in evolution.The initial transcripts H+/K+ ATPase were detected in 22 days post hatching(dph),after gastric glands(16 dph) were formed.This suggested that the morphologic development of gastric glands was not synchronous with their functional development.In addition,H+/K+ ATPase mRNAs were expressed highly in esophagus.We surmised that the turbot stomach was reduced to a dilatation of esophagus,and that esophagus retained its ability to express pepsinogen.The distribution of tPGA and tPGC transcripts in the turbot was investigated using in-situ hybridization.The results show that tPGA and tPGC mRNA were first detected in the esophagus and cardiac region of the stomach.This study provided a basis for understanding the digestive mechanisms in teleost.