Growth of artificially fed infant rats: effect of supplementation with insulin-like growth factor I.
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.
Philipps
A F
AF
Department of Pediatrics, University of Arizona, College of Medicine, Tucson, Arizona, USA.
Anderson
G G
GG
Dvorák
B
B
Williams
C S
CS
Lake
M
M
Lebouton
A V
AV
Koldovský
O
O
D000818:Animals; D000833:Animals, Suckling / Q000254:growth & development*; D002465:Cell Movement; D004247:DNA / Q000378:metabolism; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D007422:Intestines / Q000166:cytology; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D018970:Insulin-Like Growth Factor Binding Protein 1; D011506:Proteins; D007334:Insulin-Like Growth Factor I; D004247:DNA