Molecular Cloning, Segmental Distribution and Ontogenetic Regulation of Cationic Amino Acid Transporter 2 in Pigs

The goal of this study was to elucidate the expression and segmental distribution of the glomerular cationic amino acid metabolism transporter-2 (CAT-2) and thus to improve our understanding of porcine cationic amino acid transporters and amino acid absorption.Porcine CAT-2 was cloned, sequenced and characterized.The predicted amino acid sequence of porcine CAT-2 shared 86.1% and 92.1% identity with human and mouse CAT-2A, respectively.The tissue distribution patterns and ontogenic changes of CAT-2 mRNAs were determined by real-time Q-PCR.The results showed that porcine CAT-2 was highly expressed in the heart and intestinal tract (duodenum, ileum and jejunum).In addition, the mRNA of CAT-2 was found in liver, lung, kidney, brain and muscle.Within the intestinal tract, CAT-2 mRNA was most abundant in the ileum and rarely expressed in the duodenum.In the duodenum, the levels of CAT-2 mRNA reached their peak on day 7 (p<0.05)while in the jejunum, levels were low on day 1 and 7 and increased rapidly after day 26 before peaking on days 30 and 60 (p<0.05).The levels then dramatically decreased by day 90 (p<0.05).In the ileum, levels achieved their maximum on day 30 and then decreased significantly on day 60 (p<0.05).