Role of epidermal growth factor in gastroduodenal mucosal protection.

Epidermal growth factor (EGF) is a polypeptide produced in the submandibular glands, Brunner's glands, and the kidneys. The peptide is secreted in an exocrine fashion into saliva, duodenal juice, and urine. EGF stimulates cellular growth and differentiation and inhibits gastric acid secretion. Removal of the submandibular glands decreases the amount of EGF in saliva and gastric juice and subsequently the synthesis of DNA in the gastric mucosa is reduced as well as its resistance to bile-salt-induced gastric lesions. Intragastric instillation of EGF can prevent gastric ulcerations induced by aspirin as well as cysteamine in rats. EGF also accelerates the healing of chronic gastric ulcers induced by acetic acid. Cysteamine is a duodenal ulcerogen in rats. After cysteamine administration, the secretion of EGF from Brunner's glands decreases and the glands become depleted of mucus. Intraduodenal instillation of EGF can partly prevent formation of cysteamine-induced duodenal ulcers. Oral administration of EGF can accelerate healing of chronic duodenal ulcers in rats. The beneficial effect of EGF on healing of chronic gastroduodenal ulcers is probably due to the delayed effects of EGF such as stimulation of RNA and DNA synthesis. The protective effects of EGF are probably related to the early actions of the peptide such as activation of cell surface proteins and increased glycosaminoglycan synthesis.