Apical Na+-dependent neutral amino acid exchanger ASCT2 (ATB0) and mTOR-signaling components are expressed along the entire jejunal crypt-villus axis in young pigs fed a liquid milk replacer

Abstract

The Na+-dependent neutral amino acid (AA) exchanger ASCT2 (ATB0) plays an important role in the apical exchange of large neutral AAs such as glutamine (Gln) and leucine (Leu) and is essential to maintaining gut mucosal growth. The objectives of this study were to investigate expression of the ASCT2/ATB0 (SLC1A5) gene and the key mechanistic (mammalian) target of rapamycin (mTOR) signaling components in epithelia along the jejunal crypt–villus axis in young pigs fed a liquid milk replacer. Reverse transcription polymerase chain reaction (RT-PCR) analyses showed that the ASCT2/ATB0 (SLC1A5) gene mRNA abundance was higher (P 0.05) in the ASCT2/ATB0 protein abundances in the cell homogenate, the intracellular fraction, and the apical membrane among the upper villus, middle villus, and crypt cells. Abundance of phosphorylated mTOR (p-mTOR) protein was higher (P < 0.05) in the middle villus than in the uppe...