title: Systemic infusion of IGF-I or LR(3)IGF-I stimulates visceral organ growth and proliferation of gut tissues in suckling rats.
abstract: This 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.
authors.affiliation: Child Health Research Institute and Cooperative Research Center for Tissue Growth and Repair, North Adelaide, South Australia.
authors.forename: C B
authors.initials: CB
authors.lastname: Steeb
authors.forename: C A
authors.initials: CA
authors.lastname: Shoubridge
authors.forename: D R
authors.initials: DR
authors.lastname: Tivey
authors.forename: L C
authors.initials: LC
authors.lastname: Read
mesh_terms: D000367:Age Factors; D000818:Animals; D000833:Animals, Suckling; D002455:Cell Division / Q000187:drug effects; D004386:Duodenum / Q000033:anatomy & histology / Q000254:growth & development; D007082:Ileum / Q000033:anatomy & histology / Q000254:growth & development; D007328:Insulin / Q000097:blood; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives* / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000166:cytology; D007422:Intestines / Q000254:growth & development*; D008970:Molecular Weight; D009929:Organ Size / Q000187:drug effects; D051381:Rats
chemical_list: D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; C085700:long R(3)-insulin-like growth factor-I; D007334:Insulin-Like Growth Factor I