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Intravenous infusion of insulin-like growth factor I in fetal sheep reduces hepatic IGF-I and IGF-II mRNAs

journal contribution
posted on 1996-12-01, 00:00 authored by K L Kind, Julie Owens, F Lok, J S Robinson, K J Quinn, L Mundy, R S Gilmour, P C Owens
Liver contains the highest concentrations of insulin-like growth factor (IGF) I mRNA in adult rats and sheep and is a major source of circulating IGF-I. In rats, inhibition of hepatic IGF-I production by exogenous IGF-I has been reported. In fetal sheep, skeletal muscle and liver are major sites of IGF-I synthesis and potential sources of circulating IGF-I. To determine whether feedback inhibition of IGF gene expression in fetal liver or muscle by IGF-I occurs, IGF-I and IGF-II mRNAs were measured in these tissues after intravenous infusion of recombinant human IGF-I into fetal sheep. Infusion of IGF-I (26 +/- 4 micrograms.h-1.kg-1; n = 6) or saline (n = 6) commenced on day 120 of pregnancy (term = 150 days) and continued for 10 days. Plasma concentrations of IGF-I were threefold higher in infused fetuses at 130 days of gestation (P < 0.0003), whereas those of IGF-II were unchanged. IGF-I infusion reduced the relative abundance of IGF-I mRNA (P < 0.0002) and IGF-II mRNA (P < 0.01) in fetal liver by approximately 50% but did not alter IGF-I or IGF-II mRNA in skeletal muscle. These results indicate that IGF-I inhibits the expression of both IGF-I and IGF-II genes in fetal liver and that IGF gene expression in fetal liver and muscle is differentially regulated by IGF-I.

History

Journal

American journal of physiology: regulatory, integrative and comparative physiology

Volume

271

Issue

6

Pagination

R1632 - R1637

Publisher

American Physiological Society

Location

Bethesda, Md.

ISSN

0363-6119

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

1996, American Physiological Society