猪肠道碱性氨基酸转运载体(CAT1)mRNA表达的组织特异性和发育性变化

本研究旨在探讨不同品种猪肠道碱性氨基酸转运载体（CAT1）mRNA表达的组织特异性和发育规律。试验选取1、7、26、30、60、90和150日龄长白和蓝塘公猪各5头（同一品种同一日龄且体重接近），共70头，测体重后屠宰，采集十二指肠、空肠、回肠和结肠组织样品。以18S基因为内标，用实时荧光定量RT-PCR法（SYBR Green Ⅰ试剂盒）检测CAT mRNA在60日龄长白猪十二指肠、空肠、回肠和结肠表达的组织特异性，以及在长白和蓝塘猪不同日龄其十二指肠、空肠、回肠表达的发育性变化。结果显示：60日龄长白猪CAT1 mRNA的表达丰度从十二指肠到回肠呈逐渐升高的趋势，到结肠开始下降，回肠极显著高于其他3个肠段（P〈0．01），十二指肠最低；十二指肠和空肠CAT mRNA的表达在1～26d（即哺乳期）都呈上升的趋势，随后都开始有所下降；蓝塘猪十二指肠CAT1 mRNA的表达丰度在150d时显著低于其他各个阶段（P〈0．05），而长白猪90和150d都显著低于其他各阶段（P〈0．05）；空肠CAT1 mRNA的表达在26～150d各阶段都差异不显著，而26d显著高于1和7d（P〈0．05）；1～60d长白和蓝塘猪回肠CAT1 mRNA的表达都呈逐渐上升的趋势，60d后都显著下降（P〈0．05）。两品种猪不同日龄时十二指肠和空肠CAT1 mRNA的表达量都没有显著差异（P〉0．05）；长白猪回肠CAT mRNA表达在26d时显著高于蓝塘猪（P〈0．05）；在90和150d时，长白猪都显著低于蓝塘猪（P〈0．05），其他各阶段没有显著差异。结果说明，CAT mRNA在不同肠段及不同发育阶段的表达存在明显的差异，这可能与肠腔中氨基酸的浓度和氨基酸的需要水平及相关激素水平有关。

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.