ACTA VETERINARIA ET ZOOTECHNICA SINICA ›› 2017, Vol. 48 ›› Issue (3): 462-473.doi: 10.11843/j.issn.0366-6964.2017.03.009

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Study on Distribution of Free Amino Acid and Small Peptide and the Expression of Related Transporter Genes in Gastrointestinal Tract of Sheep

SUN Ya-jun, NI Zhi-he, CHEN Yu-lin, ZHANG En-ping*, WANG Yong-jun*   

  1. (College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China)
  • Received:2016-07-26 Online:2017-03-23 Published:2017-03-23

Abstract:

This study aimed to clarify quantitative distributions of free amino acids (FAA) and small peptides (PAA) in gastrointestinal tract of sheep and the mRNA expression of CAT1 (cationic amino acid transporter), EAAT3 (acidic amino acid transporter), y+LAT2, ASCT2(neutral amino acid transporters), PepT1 (small peptide transporter), APN (aminopeptidase) and DPEP2 (dipeptidase) in gastrointestinal tract of sheep. A total of 6 healthy Small-tail Han sheep at the age of 18 months were slaughtered to collect chyme and tissues of rumen, duodenum, jejunum, ileum and cecum. Then concentrations of the most of FAA and PAA in supernatant of chyme were detected and the mRNA expression of related genes were quantified by RT-PCR. The results showed that: 1) The concentrations of the most of FAA from high to low was jejunum, duodenum, ileum, rumen, cecum. The concentrations of FAA in jejunum and duodenum were significant higher than that in other parts(P<0.05). Proportions of FAA in these parts were different. The concentrations of the most of PAA from high to low was duodenum, jejunum, ileum, cecum, rumen. Except for cecum and rumen, they were significant different from each other(P<0.05). Proportions of PAA in these parts were different. The proportion of PAA in total amino acids was the significantly lowest in jejunum(P<0.05). 2) CAT1 mRNA in jejunum had the highest abundance, but there were no significant difference among 5 parts. EAAT3, y+LAT2, PepT1 and APN mRNA had a similar expression pattern that they all had the highest abundance in ileum. ASCT2 mRNA had the highest abundance in duodenum, and DPEP2 mRNA had the highest abundance in cecum. Results indicate that concentrations and proportions of FAA in these parts are different, the same as PAA. The major secretion site of FAA is jejunum. The major absorption site of FAA is ileum. The major production site of PAA is duodenum. The major digestion site of FAA is jejunum. The major absorption site of FAA in mesenteric system is ileum. The absorbility of cationic amino acids in 5 parts are similar. Acidic amino acids and the most of neutral amino acids are absorbed major in ileum, but some of neutral amino acids are absorbed major in jejunum. This study provides the theory basis for amino acid nutrition in small intestine of sheep and for digestion and absorption regular pattern of protein of sheep.

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