Skip to main content
ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Biosciences & Biotechnology Laboratory » Research » Publications at this Location » Publication #310299
Title: The mRNA expression of amino acid transporters, aminopeptidase, and the di- and tri-peptide transporter PepT1 in the intestine and liver of post-hatch broiler chicks

Author
item Miska, Kate
item Fetterer, Raymond
item WONG, ERIC - Virginia Tech

Submitted to: Poultry Science Review
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2015
Publication Date: 6/1/2015
Citation: Miska, K.B., Fetterer, R.H., Wong, E.A. 2015. The mRNA expression of amino acid transporters, aminopeptidase, and the di- and tri-peptide transporter PepT1 in the intestine and liver of post-hatch broiler chicks. Poultry Science Review. 94(6):1323-1332.

Interpretive Summary: The mRNA expression profile for eleven amino acid transporters (AAT), the di-and tri- peptide transporter (Pept1), and aminopeptidase N (APN) during post-hatch growth was determined. Birds were sampled at days 1, 3, 5, 7, 10, 14, 71, and 21 days following hatch. Five birds were sampled at each time period. Three segments of the small intestine: duodenum, jejunum, and ileum, a portion of the large intestine (the ceca), as well as the liver were sampled. The highest gene expression was observed in the small intestine. This is not surprising since small intestine is responsible for most of the nutrient absorption. In the small intestine the expression of the genes associated with the gut lumen was more dynamic than the expression of the genes associated with the basolateral surface that is contact with circulation. This could be due to changes in nutrient content in the gut. Gene expression in the ceca was observed but it was much lower than that of the small intestine, and the expression of the genes associated with the lumen decreased over sampling time, although the expression of the genes associated with the basolateral surface remained steady. It is possible that the capacity of the ceca in transportation of amino acids decreases with age. The liver is highly metabolically active and it is responsible for synthesis of most proteins present in the blood, therefore it should express components of the amino acid processing and transport system. It was found that gene expression of most of the AATs was detectable but at lower levels than seen in the small intestine. Shortly after hatch, young chicks are fed a diet that is high in protein (containing corn and soybean meal) and the current data suggest that at hatch chicks are ready to process and absorb these nutrients in the gut as well as the liver.

Technical Abstract: Amino acid transporter (AAT) proteins are responsible for the movement of amino acids (AA) in and out of cells. Aminopeptidase (APN) cleaves AAs from the N terminus of polypeptides making them available for transport, while PepT1 is a di- and tri- peptide transporter. In the intestine, these proteins are present on the brush border and basolateral membranes of enterocytes, and are essential for the uptake of AAs into enterocytes and their release into circulation. The purpose of this study was to determine the level of transcription of these genes after hatch in three regions of the small intestine: duodenum, jejunum, and ileum, as well as ceca and liver. Five heritage broiler chicks were sampled at day after hatch and days 3, 5, 7, 10, 12, 14, 17, and 21 post-hatch, and mRNA expression level was measured using absolute quantitation. The small intestine (duodenum, jejunum, ileum) expressed the largest quantities of each gene tested. In general, the expression in the ceca and liver was 1-3 magnitudes less than that of the small intestine. The expression of basolateral transporters in the small intestine was more constant over days post-hatch than the expression of brush border transporters. PepT1 expression in the ceca was absent and the expression of the other brush border transporters decreased over the sampling period, while expression of basolateral genes was relatively constant over the sampling period. In the liver the expression of PepT1 fell to undetectable levels by day 5 post hatch, and BoAT could not be detected at any of the time-points; while the expression of bo,+AT, EAAT3, and rBAT significantly decreased at 12 days post hatch compared to day 1 post hatch. However, the expression of CAT1, CAT2, SNAT1, and SNAT2 significantly increased at day 5 post-hatch compared to day 1 and these levels remained throughout the rest of the sampling period. The current results suggest that at one day post-hatch chicks are capable of AA processing and transport in the intestine as well as the liver. Additionally the ability of the ceca in transporting AA from the lumen may decrease with age. The liver should be capable of AAT, but its capabilities may be more specific since the expression of several transporters in this organ is either absent or very low.