The Na+‐neutral amino acid transporter ASCT2 gene is down‐regulated along the jejunal crypt‐villus axis quantified by real‐time RT‐PCR in formula‐fed neonatal pigs

Abstract

The Na+-neutral amino acid (AA) transporter ASCT2 gene expresses ATB0 protein responsible for the uptake of luminal neutral AA across the apical membrane. The study was to quantify the ASCT2 mRNA expression along the jejunal crypt-villus axis in six Yorkshire gilts at 14-16 d of age fed a milk-based liquid formula. Three epithelial cell fractions, representing cells from the upper villus, the middle villus and the crypt regions, were sequentially isolated, with cell viability of 92–95% as assessed by trypan blue exclusion, along the crypt-villus axis from the entire jejunum by the distended sac method. The 526-bp partial mRNA sequence of the porcine neutral AA transporter ASCT2 gene, obtained according to the conserved region of the human gene, showed 90 and 84% homology with the human and mouse sequences, respectively. Real time RT-PCR analyses (SmartCycler using SYBR Green-I detection kit) revealed a linear decrease (P<0.05) in the ASCT2 mRNA level from the crypt cell, to the middle villus cell and the upper villus cell with β-actin as the house-keeping control. These results suggest that ASCT2 gene expression is down-regulated from the small intestinal crypt to the villus cells at in the formula-fed neonatal pig.