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

表皮生长因子(EGF)存在于各种种类的牛奶中。老鼠奶中含有35-40纳克/毫升的表皮生长因子。相比之下，婴儿配方奶粉中不含表皮生长因子。为了阐明乳源性EGF在新生大鼠胃肠道发育中起重要作用的假说，采用人工饲养技术，给乳鼠饲喂新乳代乳剂、不含生长因子的蒸发乳白蛋白(EMA)或添加EGF(100 ng/ml)的EMA 4d或8d。结果表明，在EMA-EGF(+)饲养的大鼠中，体重增长和尾长与EMA-EGF(-)饲养4d或8d无显著差异。在4天的饲养试验中，两组大鼠的胃和小肠脏器重量、蛋白质和DNA含量相似。饲喂EMA-EGF(-)饲料的大鼠血清EGF水平和肠道EGF含量均显著降低。胃排空和肠道转运的测量结果表明，乳载EGF对胃肠动力没有影响。这些结果与我们之前的观察一致，即短期口服EGF对肠道运动没有立竿见影的效果(Shinohara数据)。此外，皮下注射EGF后血清EGF水平即刻升高。这些结果表明，EGF对胃肠动力的影响主要是通过肠外给药来调节的。长期给EGF对蔗糖酶比活性、蔗糖酶异麦芽糖酶mRNA水平和乳糖酶根茎苷mRNAs水平没有影响。从目前的研究来看，用转化生长因子-β饲喂EMA的动物并不能得到很好的结果，未来的研究计划探讨乳载转化生长因子-β在胃肠道功能发育中的生理作用。

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.