Developmental expression of transforming growth factor-alpha in the upper digestive tract and pancreas of the rat

This study was designed to examine the developmental expression and the localization of the transforming growth factor alpha (TGF-alpha) in the upper gastrointestinal tract and pancreas of the rat. Immunohistochemical techniques using an antibody against rat TGF-alpha were performed on the stomach, duodenum and pancreas of fetuses (19 to 21 days of gestation), of pups during the suckling period (days 0 to 13 postpartum) and after weaning (day 25 postpartum) and of adults. The temporal appearance of TGF alpha varied depending on the tissues. In the antral mucosa it likely appeared before 19 days of gestation. In this tissue, the immunostaining was intense from 20 days of gestation and did not decline after birth. In the duodenum, the TGF alpha immunoreactivity was definitely present with a high intensity at 20 days of gestation in villi, crypts and Brünner's glands and there after became irregular. In the fundic mucosa, TGF alpha expression was weak but clearly-established at 21 days of gestation, at least in parietal cells, and regularly increased after birth. In the pancreas, it appeared only after birth and solely in the exocrine gland. The TGF alpha immunoreactivity displayed as age progressed, first a granular pattern apparently confined in the supranuclear, i.e., Golgi area, then a diffuse cytoplasmic pattern. These findings suggest that TGF alpha may have a functional role during the developmental process of the digestive system.