SUMMARY
The factors controlling growth and maturation in the porcine gastrointestinal tract are not well understood. Epidermal growth factor (egf) is a polypeptide that has been implicated in the control of gastrointestinal tract growth, maturation, and protection in other species. Immunoreactive egf (ir-egf) and egf receptors (egf-r) were histochemically identified in formalin-fixed tissues of the upper digestive tract of 1-, 3-, 7-, 14-, 21-, and 28-day-old pigs. The ductal epithelium consistently contained ir-egf in the parotid salivary gland of pigs of all ages and in the mandibular salivary gland in pigs ≥ 7 days old. Immunoreactive egf was detected in the mucosal epithelium of the esophagus and nonglandular portion of the stomach, and in the pancreas and liver in all pigs. Gastric gland ir-egf was inconsistently detected in pigs < 14 days old and was consistently observed in all older pigs. Enterocyte egf immunoreactivity was usually weak and was variably detected in the duodenum of pigs ≤ 7 days old and in the jejunum of pigs ≤ 14 days old, but was consistently observed in older pigs. Ileal immunoreactivity was erratic. Immunoreactive egf-r were identified in the esophageal epithelium of all pigs, and in the non-glandular gastric and glandular gastric mucosa of all pigs, except for two 7-day-old pigs and one 7-day-old pig, respectively. Immunoreactive egf-r were detected in the duodenal, jejunal, and ileal enterocytes of pigs of all ages examined.