title: Stability of insulin-like growth factor I in the gastrointestinal lumen in neonatal pigs.
abstract: BACKGROUND
  Insulin-like growth factor (IGF)-I is present in the milk of various species. A prerequisite for any biological activity of milk-borne IGF-I in the suckling young is to survive the gastrointestinal luminal digestion. In the present study, the stability of IGF-I was examined in the gastrointestinal lumen in neonatal pigs.
  
  
  METHODS
  Iodine-labeled IGF-I was incubated in the gastrointestinal luminal fluids of 3-day-old suckling and 45-day-old weaned pigs at 37 degrees C for 20 minutes. Degradation of the peptide was analyzed by trichloroacetic acid (TCA) precipitation, liquid chromatography, and receptor binding assay.
  
  
  RESULTS
  IGF-I remained unchanged in the gastric fluids of suckling and weaned pigs when determined by TCA precipitation. IGF-I degraded 3%, 18%, and 37% in the luminal fluids of the proximal, mid and distal small intestine in suckling piglets compared with 53%, 62%, and 54% in weaned pigs. The results were supported by the chromatography and receptor binding analysis. Porcine colostrum had a capacity to protect IGF-I from gastrointestinal luminal digestion in weaned pigs.
  
  
  CONCLUSIONS
  Milk-borne IGF-I is stable in the gastrointestinal lumen in suckling pigs and may play a role in regulating postnatal development in the suckling young.
authors.affiliation: Department of Zoology, University of Hong Kong, Hong Kong.
authors.forename: W H
authors.initials: WH
authors.lastname: Shen
authors.forename: R J
authors.initials: RJ
authors.lastname: Xu
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D000833:Animals, Suckling / Q000378:metabolism*; D001826:Body Fluids / Q000378:metabolism; D011232:Chemical Precipitation; D002853:Chromatography, Liquid; D003126:Colostrum / Q000502:physiology; D004063:Digestion; D004064:Digestive System / Q000378:metabolism*; D004355:Drug Stability; D010450:Endopeptidases / Q000378:metabolism; D006868:Hydrolysis; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007457:Iodine Radioisotopes; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D013552:Swine / Q000378:metabolism*; D014238:Trichloroacetic Acid; D014886:Weaning
chemical_list: D007457:Iodine Radioisotopes; D014238:Trichloroacetic Acid; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D010450:Endopeptidases