Insulin-like growth factor-I (IGF-I) and IGF-binding proteins both decline in the rat during late pregnancy.
Insulin-like growth factor-I (IGF-I), IGF-II and IGF-binding proteins (IGFBP) were examined in rat serum during pregnancy and lactation. IGF-I concentrations determined after acid column chromatography of serum were low during the last third of pregnancy. IGF-II was undetectable in pregnant and non-pregnant rats. IGF-binding protein (IGFBP) concentrations, measured as high molecular mass activity in the IGF-I RIA and the IGF-II RRA of acid column fractions, paralleled the changes observed with IGF-I. Western ligand blot analysis of serum from non-pregnant rats revealed a 40-50 kDa IGFBP aligning with IGFBP-3, a smaller 28-30 kDa doublet and 24 kDa IGFBP. Serum from rats in late pregnancy lacked IGFBP-3, whereas the smaller IGFBP persisted during late pregnancy. IGFBP-3 reappeared in postpartum animals. The fall in serum IGF-I is consistent with a maternal catabolic state during late pregnancy which may maximize substrate availability for the developing fetus.
Gargosky
S E
SE
Biochemistry Department, University of Adelaide, South Australia.
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*; D002845:Chromatography; D005260:Female; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007774:Lactation / Q000097:blood; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*; D011863:Radioimmunoassay; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D013002:Somatomedins / Q000378:metabolism*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I