Steeb, C.B.Shoubridge, C.Tivey, D.Read, L.2006-06-232006-06-231997American Journal of Physiology, 1997; 272(3 Pt 1):G522-G5330002-95132163-5773http://hdl.handle.net/2440/6945This study describes developmental changes in gastrointestinal response to insulin-like growth factor I (IGF-I) peptide administration. Neonatal rats were infused with IGF-I or long [Arg3]IGF-I (LR(3)IGF-I) for 6.5 days starting on day 6 or 12 postpartum. Peptides were delivered by mini osmotic pumps at 0, 2, 5, or 12.5 microg x g(-1) x day(-1). IGF-I infusion increased plasma IGF-I levels in both age groups but stimulated body weight gain only in the older rats. Infusion of LR(3)IGF-I did not change plasma IGF-I levels. Both peptides enhanced expression of IGF-binding proteins (IGFBP) 1 and 2 and induced IGFBP-3 in the older rats. For both age groups, weights of the kidney and spleen increased by up to 85 and 76%, respectively. IGF-I treatment also stimulated gut weight and length by up to 60 and 32%, respectively, but dose dependency was observed only in the older rats. LR(3)IGF-I was more potent for all growth parameters in both age groups. Histological observations included thickening of the mucosa and muscularis externa after infusion of IGF-I peptides. Thymidine labeling in the younger rats indicated that proliferative activity increased proportionately with crypt cell growth. These results show that IGF-I peptides selectively stimulate growth of gastrointestinal tissues in suckling rats and that the proximal gut was the most peptide-responsive region.enIntestinesIntestinal MucosaDuodenumIleumAnimalsAnimals, SucklingRatsInsulinInsulin-Like Growth Factor IInsulin-Like Growth Factor Binding ProteinsOrgan SizeAge FactorsCell DivisionMolecular WeightJournal article0030005764001997133810.1152/ajpgi.1997.272.3.G522A1997WP3570001569770Shoubridge, C. [0000-0002-0157-3084]Tivey, D. [0000-0003-2213-2576]