Grimes J, Schaudies P, Davis D, Williams C, Curry B J, Walker M D, Koldovský O
Department of Pediatrics, University of Arizona, Tucson 85724.
Proc Soc Exp Biol Med. 1992 Jan;199(1):75-80. doi: 10.3181/00379727-199-43332.
Epidermal growth factor (EGF) is trophic for varying regions of the developing gastrointestinal tract (GIT) of suckling rats. The presence of large amounts of EGF in milk from various species, combined with low production of EGF by suckling animals, led to speculation that milk is a major source of EGF for suckling rats. We report that short-term fasting (8 hr) of 12-day-old suckling rats resulted in a significant decrease in the levels of immunoreactive EGF (irEGF) in the GIT. Pups refed by lactating mothers for 1 to 4 hr exhibited an increase in irEGF to original levels, whereas pups fed a rat milk substitute by gastric gavage did not have an increase in irEGF content. The irEGF levels in the GIT of pups that were manually fed normal rat milk, or rat milk substitute supplemented with EGF, returned to the prefasted levels. Fasted suckling rats refed 2 ml of rat milk in 2 h exhibited significantly higher level of irEGF in the GIT than did those refed with 0.5 ml in 45 min. Since rat milk irEGF exists in three distinct forms (A, B, and C; C is equal to authentic submandibular gland EGF, the irEGF forms in the GIT were characterized by native polyacrylamide gel electrophoresis. In the stomach luminal contents of the fed suckling rats, only the larger form, Peak B, was observed. Both the luminal content and the mucosa scrapings of all other segments of all groups contained only Form D (comigrating with desarginyl EGF), a metabolic derivative of EGF. All forms were immunoreactive, exhibited receptor binding, and stimulated DNA synthesis in growth-arrested fibroblasts. The rapid changes in EGF within the GIT of suckling rats suggest the EGF can acutely modify some GIT functions of suckling rats.
表皮生长因子（EGF）对乳鼠发育中的胃肠道（GIT）的不同区域具有营养作用。各种物种的乳汁中存在大量EGF，而乳鼠自身产生的EGF量较低，这使得人们推测乳汁是乳鼠EGF的主要来源。我们报告称，对12日龄的乳鼠进行短期禁食（8小时）会导致胃肠道中免疫反应性EGF（irEGF）水平显著下降。由哺乳期母亲重新喂养1至4小时的幼崽，其irEGF水平恢复到原始水平，而通过胃管饲喂大鼠乳替代品的幼崽，其irEGF含量并未增加。人工喂养正常大鼠乳或添加了EGF的大鼠乳替代品的幼崽，其胃肠道中的irEGF水平恢复到禁食前水平。在2小时内重新喂养2毫升大鼠乳的禁食乳鼠，其胃肠道中的irEGF水平显著高于在45分钟内重新喂养0.5毫升的乳鼠。由于大鼠乳中的irEGF存在三种不同形式（A、B和C；C等同于颌下腺来源的天然EGF），通过非变性聚丙烯酰胺凝胶电泳对胃肠道中的irEGF形式进行了表征。在喂食后的乳鼠胃腔内容物中，仅观察到较大的形式，即峰B。所有组其他所有节段的腔内容物和黏膜刮片均仅含有形式D（与去精氨酸EGF共迁移），这是EGF的一种代谢衍生物。所有形式均具有免疫反应性，表现出受体结合能力，并能刺激生长停滞的成纤维细胞中的DNA合成。乳鼠胃肠道中EGF的快速变化表明，EGF可急性改变乳鼠的一些胃肠道功能。
