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

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Conlon, M.A.; Tomas, F.M.; Owens, P.C.; Wallace, J.C.; Howarth, G.S.; Ballard, F.J.


1995-08


Journal Article


Journal of Endocrinology


146


2


247-253


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)


Human Nutrition; 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


http://joe.endocrinology-journals.org/content/146/2/247.abstract


English


0022-0795 (Print)


procite:e03ed8ed-5677-483a-ad6e-e1e7efe80e15


Conlon, M.A.; Tomas, F.M.; Owens, P.C.; Wallace, J.C.; Howarth, G.S.; Ballard, F.J. 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. Journal of Endocrinology. 1995-08; 146(2):247-253.



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