| Protein is one of three nutritent and play an important role in growth development and Metabolism of animal .intraluminal products of protein digestion are predominantly small peptides and free amino acid.Small peptides consisting of two or three amino acid are absorbed across the apical membrane of the enterocytes lining the small intestine via H+-driven peptide transporter PepT1, in contrast, free amino acids are transported across the apical membrane by several amino acid transport systems. The objectives of these studies were to investigate the distribution and ontogenetic changes of peptide transporter and amino acid transporters mRNA expression along the horizontal axis of the intestine from Tibetan sucking piglet, a trial was designed as follows:the clone of oligopeptide transporter PepT1 cDNA from Tibetan pig intestine; intestinal tissue distribution and developmental expression of oligopeptide transporter PepT1,anionic amino acid transporter EAAC1 and cationic amino acid transporter CAT1 mRNA from Tibetan sucking piglet .In trial one, jeunum tissues from 6 healthy Tibetan sucking piglets at 28 days were collected for the clone of oligopeptide transporter PepT1 cDNA by RT-PCR.It is found that it is first time to clone the ORF of oligopeptide transporter PepT1 cDNA, which has been published in Genebank with the asscession number of EU400159,predicted protein contain 708 amino acid. This sequence showed 84.4% and 81.3% homology with human and rat, respectively. The putative protein has 13 putative transmembrane domains and has a big excellar loop between 10 and 11 transmembrane domain.In trial two: 6 healthy Tibetan piglets at day 28 with similar weight body were chcsen to slaughter. Small intestinal segments samples were collected from duodenum, proximal and distal jejunums, ileum for detection intestinal tissue distribution of oligopeptide transporter PepT1, anionic amino acid transporter EAAC1and cationic amino acid transporter CAT1 mRNA abundance by Real-time PCR. The results show: 1) The abudance of PepT1 mRNA in distal jejunum was significantly higher than in duodenum, proximal jejunum and ileum(P<0.05). The Ileum had the lower expression abundance than duodenum and proximal jejunum , but it was no signifificantly difference(P>0.05). 2) There is an increased expression gradient of EAAC1 mRNA from proximal to distal intestine. Ileum had significantly higher than duodenum, proximal and distal jejunums(P<0.05). The duodenum han the lowest expression, there is no significant difference complared with proximal and distal jejunums(P>0.05). 3) Intestinal tissue distribution of CAT1 mRNA is similar with EAAC1. Expression abudance of CAT1 mRNA in ileum is highest in intestinal segment and significantly higher than in duodenum and proximal jejunum(P<0.05). In trial three:30 healthy Tibetan piglets with similar body weight(6 suckling Tibetan piglets at 1d, 7d, 14d, 21d and 28d, respectically) were chosen for detection developmental expression changes of PepT1,EAAC1 and CAT1 mRNA by real time PCR .Result show: 1)there were greater significance for ontogenesis of PepT1, EAAC1 and CAT1 mRNA expression along the horizontal axis of the small intestine of suckling Tibetal piglets. 2)Ontogenesis of PepT1 and CAT1 mRNA expression in duodenum were similar, PepT1 and CAT1 mRNA expression abundances increased gradually from d 1 to d 14 and expression were both highest at d 14, then decreased at d 21 and d 28.The expression abudance of EAAC1 mRNA at d 1 and d 7 was significantly higher than d 14,d 21 and d 28. 3) Ontogenesis of EAAC1 and CAT1 mRNA expression in jejunum were similar, EAAC1 and CAT1 mRNA expression abudance before d 14 increased gradually, then decreased at d 21, and increased at d 28; the expression abudance of Pept1 mRNA increased gradually before d 21 and then decreased slightly.3) Ontogenesis of PepT1 and CAT1 mRNA expression in ileum were similar, Pept1 and CAT1 mRNA expression abudance both were highest at d 7, then decreased significantly at d 14, and increased significantly at d 21, decreased slightly at d 28; There is an increased expression gradient of CAT1 mRNA from d 1 to d 14, then significantly decreased at d 21, and had a highest expression at d28.Conlusion there is tissue-specialthe tissue distribution expression of PepT1,EAAC1 and CAT1 mRNA along the horizontal axis of the small intestine of suckling Tibetal piglets were tissue specific. The developmental expression change of Every transporter at different intestinal segment is different, and there were greater significance for ontogenesis of PepT1,EAAC1 and CAT1 mRNA expression at any intestinal segment.
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