Immunohistochemical localization of transforming growth factor-alpha in suckling porcine intestine

The distribution of transforming growth factor-alpha (TGF alpha), a member of the epidermal growth factor (EGF) family, was studied immunohistochemically in small intestinal tissues of suckling pigs which were 7, 14 and 21 days of age. TGF alpha immunostaining was similar in villous epithelium in all intestinal regions of all ages examined, and was diffuse throughout the epithelial cytoplasm and more prominent in the apical and brush-border regions of the cells. Cytoplasmic immunoreactive TGF alpha was also identified in crypt epithelial cells; the pattern and extent of immunostaining differed among intestinal regions and ages. In all cases, the relative number of TGF alpha-immunopositive crypt epithelial cells was fewer than the number of immunonegative cells within the compartment. In duodenal and jejunal segments, relative numbers of immunopositive crypt epithelial cells were greater in 14- and 21- than in 7-day-old pigs. In all 7-day-old pigs, a relatively greater number of immunopositive epithelial cells was present in the jejunal crypts than in the duodenal crypts. Intracellular TGF alpha immunostaining was present within Peyer's patches of distal jejunum and ileum, and is a previously unreported finding. The presence of TGF alpha immunoreactive protein within small intestinal crypt epithelium has not been previously described in any species, and may be unique to suckling animals or, alternatively, the porcine species. These data suggest that TGF alpha may be an endogenous ligand for the EGF receptor in suckling porcine intestine. Increased expression of TGF alpha in suckling pigs during the period in which marked structural and functional changes occur within the small intestinal mucosa suggests a role for this growth factor in remodelling and maturation of the neonatal mucosa.