Authors : Jie Mei, Yuanqiang Zhang , Dale King , Per Sangild and Ruo Jun Xu
Abstract: Transforming growth factor-beta (TGF- ) has been detected in the milk of various species, including the pig. It has been speculated that milk-borne TGF- may play an important role in postnatal adaptation of the gut in suckling animals. However, a prerequisite for such a role is the presence of functional TGF- receptors in the gastrointestinal tract of the young. The aim of the present study was to determine if TGF- receptors are present in the small intestine in newborn pigs. The study also aimed to examine the developmental changes of TGF- receptors in the small intestine in suckling pigs. Immunohistochemical staining was used to localize the receptors in the tissue and Western blot analysis was used to determine their molecular characteristics. The level of the receptors present in the tissue was semi-quantified by a computerized image analysis and Western blot analysis. It was observed that TGF- receptors I (RI), II (RII) and III (RIII) all were widely distributed along the small intestine in newborn unsuckled pigs, and the receptors were predominantly localized at the villus epithelium. There was a significant difference in the tissue level for different receptors in newborn piglets, and there was also a significant difference for the receptor level among different regions of the small intestine. The Brunner`s glands in the duodenum of newborn piglets were strongly stained with RIII and the staining intensity in the glands reduced markedly following the onset of suckling. There was also a transient decline in the RI and RII density in the villus epithelium during the first day after birth but a marked increase in positively stained lymphocytes in the lamina propria of the intestinal villi during the immediate postnatal period. It was also observed that the staining of RI and RII at the villus epithelium shifted from the apical membrane in newborn and 3-day-old piglets to the basolateral membrane in 7- and 21-day-old pre-weaning piglets, while the staining intensity for RIII decreased markedly in 7-day-old pigs. These changes may correlate with the onset of endogenous TGF- production. The findings strongly support the hypothesis of a regulatory role of milk-borne TGF- in postnatal adaptation of the intestine in neonatal pigs.
Jie Mei, Yuanqiang Zhang , Dale King , Per Sangild and Ruo Jun Xu , 2004. Distribution and Developmental Changes of Transforming Growth Factor-beta Receptors in the Small Intestine of the Pig. Journal of Animal and Veterinary Advances, 3: 89-106.