Segmental Distribution and Ontogenetic Regulation of Cationic Amino Acid Transporter mRNA Expression in the Small Intestine of Pigs

Segmental distribution and ontogenetic regulation of cationic amino acid transporter 1(CAT1) mRNA expression was evaluated in pigs along the horizontal axis of the intestine.A total of 35 littermate purebred Lantang gilts and 35 littermate purebred Landrace gilts were divided into seven groups at the ages of d 1,7,26,30,60,90 and 150,respectively.Intestinal segments(duodenum,jejunum,ileum and colon) were collected.The CAT1 mRNA abundance was determined by real-time RT-PCR using SYBR Green I RT-PCR mix Kit.Results indicated that the CAT1 mRNA levels in Landrace pigs at day 60 were increased from the proximal to distal part of the small intestine(P 0.05) and dropped dramatically in colon(P 0.05).The ileum had the highest CAT1 mRNA abundance and the colon had the lowest.During the sucking period(day 1 to 26),the CAT1 mRNA abundances in duodenum and jejunum were increased and dropped with age after weaning.The CAT1 mRNA abundances of Lantang pigs at day 150 were significant lower than that at other ages(P 0.05) and the CAT1 mRNA abundances of Landrace pigs at day 90 and 150 were significant lower than that at other ages(P 0.05).However,there is no difference between day 26 and 150 in the jejunum CAT1 mRNA abundance.And the pigs at day 26 have a higher CAT1 mRNA abundance than that at day 1 and 7(P 0.05).For ileum,CAT1 mRNA in the Landrace and Lantang pigs increased during day 1 to 60,and then dropped(P 0.05).There is no significant difference(P 0.05) between the CAT1 mRNA abundance of Landrace and Lantang pigs in duodenum and jejunum.For ileum,the CAT1 mRNA abundance of Landrace at day 26 was significant higher than that of Lantang pigs(P 0.05),however,at day 90 and 150 were both lower than that of Lantang pigs(P 0.05).In conclusion,the mRNA expression of CAT1 was not only differentially regulated by age but also differentially distributed along the small intestine of piglets at early stages and growing stages of life,which may be related to luminal substrate concentration as well as amino acid requirement and hormone.