Abstract
IGF-I has been proposed to be an important endocrine growth factor in human fetal growth. We have determined IGF-I concentrations in acid chromalographed serum obtained in utero from 34 human fetuses of Rhesus Iso-immunized pregnancies. Furthermore, IGFBPs and their molecular weight forms in fetal serum, were investigated, to asses the bioavailabilily of circulating IGF-I. IGF-I concentrations increased significantly (r=0.52, p<0.005) from a mean of 40μg/l at 20 weeks of gestation to 75μg/l at 35 weeks and decreased (r=0.57, p<0.001) as the hemoglobin concentration decreased (range 30-140% of (he median of normal fetuses). Western ligand blot analysis of fetal serum displayed decreased IGFBP-3 and increased 1GFBP-1 and IGFBP-2 as compared to adult serum (this has been confirmed by specific RIAs). Proteoiysis of 125I IGFBP-3 was not increased in fetal serum as compared lo non-pregnant adult serum. Neutral size cromatography of pools of fetal serum displayed the presence of excess 125I IGF-I binding sites almost exclusively in the 50kDa complex. Western immunoblot analysis of the fractions displayed the following molecular weight distribution of immunoreactive IGFBP-3 (irIGFBP-3):
In conclusion there is a lack of ternary ALS/IGFBP-3/IGF-I complex formation in human fetal serum and increased IGF-I availability due to its presence predominantly in Ihe 50kDa complex or smaller forms. Furthermore, less IGF-I is bound by high affinity IGFBP-3. Finally we suggest that intra-uterine growth retardation in severe cases of Rhesus Iso-immunizalion could be attributed to decreased serum IGF-I concentrations.
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Bang, P., Rosenfeld, R., Stangenberg, M. et al. LACK OF 150kDa TERNARY COMPLEX FORMATION IN SERUM FROM THE HUMAN FETUS IN UTERO: INCREASED BIOAVAILABILITY OF CIRCULATING IGF-1. Pediatr Res 33 (Suppl 5), S72 (1993). https://doi.org/10.1203/00006450-199305001-00412
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DOI: https://doi.org/10.1203/00006450-199305001-00412