Growth of artificially fed infant rats: effect of supplementation with insulin-like growth factor I

Am J Physiol. 1997 May;272(5 Pt 2):R1532-9. doi: 10.1152/ajpregu.1997.272.5.R1532.


Insulin-like growth factor I (IGF-I), a potent mitogenic peptide, is present in considerable quantities in most mammalian milks, but its importance for the neonate is unknown. To test the hypothesis that milk-borne IGF-I is an important factor in the regulation of neonatal growth, as well as that of the gastrointestinal tract, rat pups were fed a rat milk substitute (RMS) devoid of growth factors via gastrostomy. These animals were compared with those given RMS supplemented with recombinant human IGF-I added at a concentration of 500 ng/ml. Animals given RMS + IGF-I gained mere weight than controls, although skeletal growth as represented by elongation of the tail was no different. Animals fed RMS + IGF-I had increased brain and liver wet weights as well as increased liver and small intestine protein contents. Serum IGF-I concentrations in the IGF-I-supplemented group were more than twofold above RMS controls and were similar to dam-fed rat pups. Semiquantification of serum IGF-binding proteins (IGFBP) in these animals documented that in IGF-I-supplemented pups the amount of 38- to 40-kDa molecular mass IGFBP species was also greater than in RMS controls. The rate of migration of enterocytes from crypts in duodenum and proximal jejunum was greater in IGF-I-supplemented animals than in rats fed RMS alone. These studies suggest that milk-borne IGF-I is important in modulation of somatic and gastrointestinal tract growth in the neonatal rat.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Suckling / growth & development*
  • Cell Movement
  • DNA / metabolism
  • Humans
  • Insulin-Like Growth Factor Binding Protein 1 / blood
  • Insulin-Like Growth Factor I / metabolism
  • Insulin-Like Growth Factor I / pharmacology*
  • Intestines / cytology
  • Proteins / metabolism
  • Rats
  • Rats, Sprague-Dawley


  • Insulin-Like Growth Factor Binding Protein 1
  • Proteins
  • Insulin-Like Growth Factor I
  • DNA