Administration of insulin-like growth factor-I, but not growth hormone, increases maternal weight gain in late pregnancy without affecting fetal or placental growth.
During late pregnancy in the rat, circulating levels of insulin-like growth factor-I (IGF-I) and some IGF-binding proteins (IGFBP) decline. The aim of the present study was to determine the relationship of GH to circulating IGF and IGFBP in the late-pregnant rat and to examine the effects on maternal, fetal and placental growth of preventing the decline in serum IGF and IGFBP concentrations. During the first 9 days of pregnancy, IGF-I concentrations increased from 340 to 500 micrograms/l. Recombinant human (rh) GH at 2.4 mg/kg per day and rhIGF-I at 1.4 mg/kg per day were infused into pregnant rats via osmotic mini pumps during the second half of pregnancy. After pump implantation on day 11 of pregnancy, only IGF-I infusion significantly increased circulating IGF-I. A maximum IGF-I concentration of 907 micrograms/l was measured on day 14 during treatment with IGF-I, after which the serum concentration decreased to 510 micrograms/l by day 20 of pregnancy. The serum IGFBPs were examined using a Western ligand blot technique. Infusion of neither GH nor IGF-I returned the IGFBPs to non-pregnant levels. Administration of IGF-I slightly increased IGFBP-3 and a smaller 32 kDa IGFBP at days 17 and 20 of pregnancy. Neither fetal nor placental weight was significantly different between treatment groups. However, administration of IGF-I significantly increased maternal weight gain during the 10-day treatment period.(ABSTRACT TRUNCATED AT 250 WORDS)
Gargosky
S E
SE
Department of Biochemistry, University of Adelaide, South Australia.
Owens
J A
JA
Walton
P E
PE
Owens
P C
PC
Wallace
J C
JC
Ballard
F J
FJ
D000818:Animals; D015153:Blotting, Western; D002352:Carrier Proteins / Q000097:blood; D005314:Embryonic and Fetal Development / Q000187:drug effects*; D005260:Female; D005333:Fetus / Q000033:anatomy & histology / Q000187:drug effects; D013006:Growth Hormone / Q000494:pharmacology*; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D009929:Organ Size / Q000187:drug effects; D010920:Placenta / Q000187:drug effects*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011994:Recombinant Proteins / Q000494:pharmacology; D015430:Weight Gain / Q000187:drug effects*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone