摘要
已有的研究表明，消化道可以小肽的形式吸收氨基酸，但尚未很好地确定小肽的主要吸收部位。我们在另一项研究中对牛Ⅰ型肽载体（BPepTⅠ）第3～10结构域1566bp片段序列进行了测定（Genebank登录号：DQ309694），与绵羊相同区域片段序列同源性高达96．04％。本研究以BPepⅠ测序结果为基础，并参考绵羊的部分序列设计了跨内含子引物，荧光实时定量聚合酶链反应（RT-PCR）方法测定了牛离体各段消化道黏膜或上皮组织BPepTⅠ的相对表达水平，以评估小肽在牛消化道的主要吸收部位。以持家基因β-actin为参比基因，结肠样品为校正样品（其相对表达量2^-△△CT值为1），研究结果表明：在整段消化道中，BPepTⅠ的相对表达量（2^-△△CT值）由高到低依次为回肠（30．62）、空肠（26．12）、瓣胃（22．61）、瘤胃（16．17）、十二指肠（11．97）、网胃（5．18）、皱胃（3．22）、盲肠（1．13）和结肠（1．00）。各段消化道BPepTⅠ相对表达量差异显著（P〈0．05），其中回肠相对表达量与空肠和瓣胃差异不显著（P〉0．05），与瘤胃、十二指肠、网胃、皱胃、盲肠、结肠差异显著（P〈0．05）；空肠相对表达量与瓣胃、瘤胃、十二指肠差异不显著（P〉0．05），与网胃、皱胃、盲肠、结肠差异显著（P〈0．05）；网胃、皱胃、盲肠、结肠的2^-△△CT值均在5．2以下，相互之间相对表达量的差异不显著（P〉0．05）。由BPepTⅠ基因相对表达活性可以将牛的各段消化道分为3组，回肠、空肠、瓣胃的活性最高，其次为瘤胃和十二指肠，网胃、皱胃、盲肠、结肠则；。
It was well documented that part of the amino acids in the digesta could be absorbed in the form of small peptide, but which part （parts） of the GI tract absorb small peptide most activelly still need to be revealed. We have sequenced a 1 566 bp segment from the 3^rd to the 10^th domains of bovine peptide transporter Ⅰ （BPepT Ⅰ ）in a previous study （Genebank accession No.： DQ309694）, which has 96.04% similarity with the corresponding segment of sheep by homology analysis. A cross intron primer was designed based on the sequenced segment of BPepT Ⅰ and the sequence of sheep peptide transporter Ⅰ in the present study. The relative expression level of BPepT Ⅰ in the mucosa or epithelium of different parts of the GI tract of cattle was measured in vitro by RT-PCR techniques. Using housekeeping gene β-actin as the internal control and colon mucosa as the calibrator sample [the relative amount of gene expression （2^-△△CT value） was set to 1], the results revealed that the relative expression levels （2^-△△CT value） of BPepT Ⅰ differed （P〈0.05） in mucosa from different parts of the GI tract of cattle. The 2^-△△CT values from the highest to the lowest was the lieac mucosa （30.62）, jejunal mucosa （26.12）, omasal epithelium （22.61）, ruminal epithelium （16.17）, duodenal mucosa （11.97）, reticular epithelium （5.18）, abomasal mucosa （3.22）, cecal mucosa （1.13）, and colonic mucosa （1.00）. Results of Duncan＇s multiple range test indicated that the 2^-△△CT value of ileum mucosa differed insignificantly with those of jejunal mucosa and omasal epithelium （P〉0.05）, but differed significantly with the other 2^-△△CT values （P〈0.05）; the 2^-△△CT value of jejunum mucosa differed insignificantly with those of omasal epithelium, rumen epithelium, and duodenum mucosa （P〉0.05）, but differed significantly with those of reticular epithelium, abomasal mucosa, and colonic mucosa （P〈0.05）. The 2^-△△CT values of reticular epithelium, abomasal mucosa, cecal mucosa, and colonic mucosa were below 5.2, and the difference among them was insignificant （P〉 0. 05）. We proposed that the relative expression levels of different parts of the GI tract of cattle could be grouped into three categories based on their 2^-△△CT value measured, The highest group includes ileum, jejunum, and omasum; the medium group includes rumen and duodenum; and the lowest group includes reticulum, abomasum, cecum, and colon.
出处
《动物营养学报》
CAS
CSCD
北大核心
2008年第2期183-190,共8页
CHINESE JOURNAL OF ANIMAL NUTRITION
基金
山东省奶牛良种工程项目资助
