Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig

J Endocrinol. 1995 Aug;146(2):247-53. doi: 10.1677/joe.0.1460247.


We have tested whether an animal with substantial amounts of both IGF-I and IGF-II in circulation, such as the guinea pig, would respond to chronic IGF infusion in the same manner as the adult rat, which has negligible amounts of IGF-II in blood. Female guinea pigs of 350 g body weight were continuously infused for 7 days with recombinant guinea pig IGF-I or -II (120 or 360 micrograms/day) or long R3 IGF-I (LR3IGF-I) (120 micrograms/day), an analogue which has much reduced affinities for IGF binding proteins. IGF-I or IGF-II infusion led to substantial increases in plasma IGF-I or IGF-II respectively in comparison with vehicle-infused animals. Nevertheless, body weight gain, feed intake, feed conversion efficiency and carcass composition were not significantly affected by any treatment (significance was deemed to be P < 0.05). Amongst the tissues examined only the fractional weight (g/kg body weight) of the adrenals was increased, and that only by the higher dose (360 micrograms/day) of IGF-I. However, the fractional weight of adrenals, gut, kidneys and spleen were significantly increased by LR3IGF-I, but again overall growth was not stimulated. A possible explanation for the lack of IGF-I effects is that total circulating IGF concentrations were not increased by these treatments. IGF-II significantly raised total IGF concentrations at the higher dose only. Plasma IGF-I was reduced by IGF-II infusion, as was plasma IGF-II by IGF-I infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Glands / anatomy & histology
  • Animals
  • Female
  • Guinea Pigs
  • Insulin-Like Growth Factor Binding Protein 1 / metabolism*
  • Insulin-Like Growth Factor I / analogs & derivatives*
  • Insulin-Like Growth Factor I / metabolism
  • Insulin-Like Growth Factor I / pharmacology
  • Insulin-Like Growth Factor II / metabolism
  • Insulin-Like Growth Factor II / pharmacology
  • Intestines / anatomy & histology
  • Kidney / anatomy & histology
  • Organ Size / drug effects*
  • Somatomedins / metabolism*
  • Spleen / anatomy & histology


  • Insulin-Like Growth Factor Binding Protein 1
  • Somatomedins
  • long R(3)-insulin-like growth factor-I
  • Insulin-Like Growth Factor I
  • Insulin-Like Growth Factor II