Intestinal Trefoil Factor (ITF or TFF3), a member of the newly recognized trefoil factor family (TFF), is secreted normally and abundantly at the mucosal surface by goblet cells throughout the small and large intestine in adults. The distinct three-looped secondary structure formed by intra-chain disulfide bonds contributes to the unique stability of TFF peptides in the harsh environment of the gastrointestinal lumen. ITF has been recently shown to play important roles in the maintenance and repair of the intestinal mucosal barrier (Mashimo H, et al. Science 1996;274:262-265). Since disruption of the mucosal barrier or mucosal injury is an important event in the development of necrotizing enterocolitis (NEC), a relative lack of ITF in premature infants may increase their susceptibility to intestinal mucosal injury or NEC. To study the expression of ITF during intestinal development, whole intestinal tissues were collected from rats at different developmental stages (gestational day 14, 17, 20 and postnatal day 1, 7, 17, 24 and adult). Total intestinal RNA was extracted by lithium chloride ultracentrifugation for Northern blot analysis and some of the tissues were also fixed in formalin for immunohistochemistry staining (the rITF cDNA and the anti-rITF antibody were kindly provided by Dr. D.K. Podolsky, Boston, MA). The results show that rat ITF mRNA expression was not detected by Northern blot analysis until the 17th gestational day (term=22days), expression was greater on gestational day 20 and was further increased following weaning on postnatal day 24. The ITF peptide was first detected in intestinal mucosal tissue by immunohistochemistry on gestational day 20 in maturing goblet cells and was present in the goblet cells at all later time points. Conclusion: Significant expression of ITF in rats begins late in gestation (days 17-20 of gestation). We speculate that expression of ITF in human may also be developmentally regulated and the ITF expression may be relatively deficient in premature infants. These data suggest that ITF may have a role in the etiology and pathogenesis of NEC in premature infants.