Department of Animal Science, Michigan State University, East Lansing 48824, USA.
J Anim Sci. 2010 Mar;88(3):1028-33. doi: 10.2527/jas.2009-2406. Epub 2009 Nov 20.
To test the hypothesis that AA transporter transcripts are present in the large intestine and similarly expressed along the intestinal tract, mRNA abundance of candidate AA transporter genes solute carrier (SLC) family 7, member 9 (SLC7A9), SLC7A1, SLC7A8, and SLC43A1 encoding for b(0,+)-type AA transporter (b(0,+)AT), cationic AA transporter-1 (CAT-1), L-type AA transporter-2 (LAT-2), and L-type AA transporter-3 (LAT-3), respectively, was determined in small and large intestinal segments of the horse. Mucosa was collected from the equine small (jejunum and ileum) and large intestine (cecum, left ventral colon, and left dorsal colon), flash frozen in liquid nitrogen, and stored at -80 degrees C. Messenger RNA was isolated from tissue samples, followed by manufacture of cDNA. Relative quantitative reverse transcription-PCR was conducted using the 2(-DeltaDeltaCT) method, with glyceraldehyde-3-phosphate dehydrogenase serving as the housekeeping gene. Compared with the jejunum, cationic and neutral AA transporter SLC7A9 mRNA abundance was similar in the ileum, cecum, and large intestinal segments. Compared with the jejunum, cationic AA transporter SLC7A1 mRNA abundance was similar in the ileum and decreased in the cecum, left ventral colon, and left dorsal colon (P < 0.001). Neutral AA transporter SLC7A8 mRNA abundance decreased from the cranial to caudal end of the intestinal tract (P < 0.001). Neutral AA transporter SLC43A1 mRNA abundance was similar in the ileum and left dorsal colon and increased in the cecum (P < 0.01) and left ventral colon (P < 0.1) compared with the jejunum. Cationic and neutral AA transporter SLC7A9 mRNA abundance was similarly expressed in the large compared with small intestine, whereas cationic AA transporter SLC7A1 was of low abundance in the large intestine; neutral AA transporters SLC7A8 and SLC43A1 were differentially expressed with decreased abundance of SLC7A8 and increased abundance of SLC43A1 in the large intestine. Results indicate that the large intestine might contribute to both cationic and neutral AA uptake and absorption predominantly via transporters LAT-3 and b(0,+)AT.
为了检验 AA 转运体转录本存在于大肠并沿肠道相似表达的假设，候选 AA 转运体基因溶质载体（SLC）家族 7，成员 9（SLC7A9）、SLC7A1、SLC7A8 和 SLC43A1 的 mRNA 丰度被测定，它们分别编码 b(0,+)-型 AA 转运体（b(0,+)AT）、阳离子 AA 转运体-1（CAT-1）、L 型 AA 转运体-2（LAT-2）和 L 型 AA 转运体-3（LAT-3）。马的小肠（空肠和回肠）和大肠（盲肠、左腹结肠和左背结肠）的黏膜从马身上采集，液氮中冷冻，并储存在-80°C 下。从组织样本中分离出信使 RNA，然后制造 cDNA。采用 2(-DeltaDeltaCT)法进行相对定量逆转录-PCR，以甘油醛-3-磷酸脱氢酶作为管家基因。与空肠相比，回肠、盲肠和大肠段的阳离子和中性 AA 转运体 SLC7A9 mRNA 丰度相似。与空肠相比，阳离子 AA 转运体 SLC7A1 mRNA 丰度在回肠中相似，但在盲肠、左腹结肠和左背结肠中降低（P<0.001）。中性 AA 转运体 SLC7A8 的 mRNA 丰度从肠道的颅侧到尾侧降低（P<0.001）。回肠和左背结肠的中性 AA 转运体 SLC43A1 mRNA 丰度相似，与空肠相比，盲肠（P<0.01）和左腹结肠（P<0.1）增加。阳离子和中性 AA 转运体 SLC7A9 的 mRNA 丰度在大肠中与小肠相似表达，而阳离子 AA 转运体 SLC7A1 在大肠中的丰度较低；中性 AA 转运体 SLC7A8 和 SLC43A1 的表达不同，SLC7A8 的丰度降低，SLC43A1 的丰度增加。结果表明，大肠可能主要通过 LAT-3 和 b(0,+)AT 参与阳离子和中性 AA 的摄取和吸收。
