The role of EGF,TGF-beta on developing gastrointestinal tract in artifically-rearing rats.

表皮生长因子（EGF）存在于不同种类的牛奶中。大鼠乳中EGF含量为35-40 ng/ml。相比之下，婴儿配方奶粉中不含EGF。为了阐明乳源性EGF在新生儿胃肠道发育中发挥重要作用的假设，采用人工饲养技术，对哺乳大鼠进行了为期4天或8天的人工饲养，分别饲喂不含生长因子的新型大鼠乳代用品蒸发乳白蛋白（EMA）或添加EGF （100 ng/ml）的EMA。我们的研究结果显示，在4天和8天的研究期间，EMA-EGF（+）喂养大鼠的体重增加和尾长与EMA-EGF（-）喂养大鼠没有显著差异。饲养4d时，两组仔猪胃、小肠脏器重量、蛋白质和DNA含量基本一致。饲喂EMA-EGF（-）日粮的大鼠血清EGF水平和肠道EGF含量均显著降低。胃排空和肠道运输的测量结果表明，乳源性EGF对胃肠运动没有影响。这些结果与我们之前的观察一致，即短期口服EGF对肠道运动没有直接影响（Shinohara数据）。此外，皮下给药EGF还伴随着血清EGF水平的立即升高。这些结果表明，EGF在体内对胃肠运动的影响主要是由肠外给药EGF调节的。长期给药EGF对蔗糖酶比活性、蔗糖-异麦芽糖酶mRNA和乳糖-苯丙素mRNA水平没有影响。从目前的研究来看，我们还不能从给EMA动物喂食tgf - β得到确切的结果，未来的研究将进一步探讨乳源性tgf - β对胃肠道功能发育的生理作用。

Epidermal growth factor (EGF) is present in milk from various species. Rat milk contains 35-40 ng/ml of EGF.In contrast, EGF is absent in infant formulas. To clarify the hypothesis that milk-borne EGF plays an important role in the neonatal development of the gastrointestinal tract, suckling rats were fed either new rat milk substitute, Evaporated Milk Albumin (EMA) free of growth factors or EMA supplemented with EGF (100 ng/ml) for 4 day or for 8 days, utilizing an artificial ly-rearing technique.The results from our studies showed that in EMA-EGF(+) feeding rats, body weight gain and tail length were not significantly difference from EMA-EGF(-) feeding rats for 4 days or 8 days study period. For 4days feeding study, organ weights of stomach and the small intestine, content of protein and DNA were similar between two groups. Rats fed EMA-EGF(-) diet had markedly decreased serum EGF levels and intestinal EGF content. Results from measurements of gastric emptying and intestinal transit have shown that milk-borne EGF bad no effect on gastrointestinal motility. These results are agreement with our previous observation that short term orogastrically administered EGF has no immediate effect on intestinal motility (Shinohara data). Moreover the subcutaneous administration of EGF was accompanied by an immediate increase in serum EGF levels These results indicate that the EGF in vivo effects on gastrointestinal motility is regulated predominantly by parenteral administration of EGF.Eternal administration of EGF did not affect on sucrase specific activity, levels of sucrase-isomaltase mRNA and lactase-phlorizin mRNA.From present study we could not get dear results from animal fed EMA with TGF-beta, future studies are planned to address the physiological role of milk-borne TGF-beta on developing gastrointestinal tract function.