Infusion of human insulin-like growth factor I (IGF-I) into malnourished rats reduces hepatic IGF-I mRNA abundance.
To determine whether the serum level of IGF-I influences its hepatic synthesis through negative feedback regulation, we infused 200 micrograms/d of human IGF-I subcutaneously into young male rats eating either an energy-restricted or ad lib diet. In energy-restricted rats, a two-fold increase in serum IGF-I concentration produced a 41% increase in growth rate at the end of one week, and a 30% decrease in steady state hepatic IGF-I mRNA and 56% drop in serum GH at the end of two weeks. In ad lib fed rats, the increased serum IGF-I concentration neither enhanced growth rate nor significantly reduced hepatic IGF-I mRNA abundance or serum GH levels. These data suggest that the abundance of hepatic IGF-I mRNA in energy-restricted rats is controlled, in part, by serum IGF-I levels via negative feedback regulation.
Schalch
D S
DS
Department of Medicine, University of Wisconsin, Madison.
Yang
H
H
Ney
D M
DM
DiMarchi
R D
RD
D000818:Animals; D004734:Energy Metabolism / Q000187:drug effects; D006128:Growth / Q000187:drug effects; D013006:Growth Hormone / Q000097:blood; D007260:Infusion Pumps; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009748:Nutrition Disorders / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013002:Somatomedins / Q000008:administration & dosage*
D012333:RNA, Messenger; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone