【作者】 霍永久；

【导师】 王恬；

【作者基本信息】 南京农业大学 ， 基础兽医学， 2005， 博士

【摘要】 乳源性活性肽对胃肠道的发育可能有重要的营养与调节作用，但调节机制不清楚。本研究探索了母乳、胎儿宫内发育迟缓(intrauterine growth retardation，IUGR)、乳源性胰岛素和酪蛋白酶解产物乳源活性肽对新生仔猪小肠发育影响及其作用机理。 本研究包括五个部分。 第一部分研究了自然哺乳新生仔猪小肠黏膜及肝脏部分基因表达水平的变化。随机选取10头初生仔猪(长白×大约克×米猪)，分到新生组(D0)和母猪哺乳3天组(D3)，每组各5头。D0仔猪在生后2～4h内屠宰取样，D3组仔猪在母猪喂养3天后屠宰取样。结果表明，D3组仔猪小肠长度与重量、黏膜重、黏膜DNA、RNA和蛋白质含量以及乳糖酶、麦芽糖酶和氨基肽酶活性高于D0组(P＜0.05或P＜0.01)，D3组小肠黏膜IGF-I及其受体和LAP基因mRNA水平高于D0组(P＜0.05)。D3组肝脏IGF-I的基因表达高于D0组(P＜0.01)。结果提示：新生仔猪的肠道的迅速发育与黏膜IGF-I受体和IGF-I基因的上调以及肝脏IGF-I基因表达的上调有关，LAP活性的增加部分原因是是该基因表达水平提高。 第二部分研究了IUGR对新生仔猪胃肠道发育的影响。选取新生苏太仔猪5窝，每窝选IUGR(初生体重低于群体平均值2SD)和正常仔猪(初生体重低于群体平均值1SD)各1头，分别分至IUGR仔猪组(实验组)和正常仔猪组(对照组)。生后不哺乳，2～4h内屠宰取样。结果表明，实验组仔猪胃重、小肠重和小肠黏膜重均低于(P＜0.01)对照组。实验组小肠和结肠长度低于(P＜0.05)对照组。IUGR仔猪肠黏膜胰岛素受体和GH受体基因mRNA水平有低于正常仔猪的趋势(P值分别为0.17和0.11)，IGF-I基因mRNA水平显著低于(P＜0.05)正常仔猪。结果提示：IUGR新生仔猪小肠重量显著低于正常仔猪，这可能与IUGR仔猪肠黏膜IGF-I基因mRNA丰度较低有关。 第三部分研究了胰岛素(实验一)和酪蛋白酶解产物(实验二)对新生仔猪肠道生长和组织形态学的影响。实验一：选择5头初生苏大仔猪，生后立即屠宰取样，作为新生对照组(N)。另外，从五窝初生仔猪中选出10头仔猪，每窝选出2头，分别分到饲喂牛乳处理组(M)(n=5)和牛乳中添加胰岛素处理组(MI)(n=5)，胰岛素添加量为2.5mg／L。M组和MI组仔猪出生后人工喂养3天，3h喂饲一次(30mL／kg更多还原

【Abstract】 Studies in recent years found that the milk-borne bioactive peptides might regulate the development of gastrointestinal tract, however, its mechanism remains unknown. We studied the effect of naturally suckling, intrauterine growth retardation, insulin and pre-hydrolyzed casein, on some growth-related gene expressions in the tissue of small intestine and liver to explore the underground mechanism of the regulation effect of the bioactive peptides on the intestinal development.Our studies included five sections presented as follows:In section one, we explored the underground mechanism of the rapid development of gastrointestinal tract in neonatal pigs. Ten newborn piglets were selected and divided into group 1 (D0, n=5) and 2 (D3, n=5). The piglets of DO were slaughtered within 2~4 hours after birth and those of D3 were reared by sows for three days and then slaughtered. The contents of DNA, RNA, and protein, the activities of lactase, maltase and L-leucine aminopeptidase (LAP) were determined. The expressions of receptors for growth hormone (GH), insulin and insulin-like growth factor I (IGF-I), IGF-I and LAP in the intestinal mucosa, GH receptor and IGF-I in the liver were quantified by the method of RT- PCR. The results showed that the length and the weight of small intestine, the contents of DNA, RNA, and protein, the activities of lactase, maltase and LAP in the small intestinal mucosa of DO were higher (P<0.05 or P<0.01) than that of D3. In the mocosa of small intestine, expressions of IGF-I receptor, IGF-I and LAP in D3 were higher than that of D0. In liver, the expression of IGF-I in D3 was up regulated (P<0.01) compared with D0. These results suggest that the fast development of gastrointestinal tract in neonatal pigs is related to the up-regulation of IGF-I receptor, IGF-I expression in the small intestinal mucosa, and also may be related to the up-regulation of IGF-I expression in the liver. The increase of LAP activity is partially the result of up-regulation of LAP gene expression.In section two, we examined the influences of intrauterine growth retardation (IUGR)更多还原