AJP - Endocrinology and Metabolism, Vol 263, Issue 6 E1151-E1156, Copyright © 1992 by American Physiological Society
Effects of acute hypoxemia on insulin-like growth factors and their binding proteins in fetal sheep
H. S. Iwamoto, M. A. Murray and S. D. Chernausek
Children's Hospital Research Foundation, University of Cincinnati, Ohio 45229-2899.
It has been proposed that insulin-like growth factor I (IGF-I) regulates
fetal growth and differentiation. Plasma IGF-I concentrations correlate
positively with fetal nutrient availability and newborn birth weights. To
explore the hypothesis that hypoxemia decreases fetal growth by decreasing
fetal IGF-I availability, we instrumented 14 fetal sheep with vascular
catheters. At least 4 days after surgery, 10 fetuses were made acutely
hypoxemic by infusing nitrogen into the maternal trachea for 3 h. Fetal
blood oxyhemoglobin saturation decreased from 53 +/- 6 (SD) to 31 +/- 9%.
Concomitantly, plasma IGF-I concentrations decreased from 91 +/- 11 to 67
+/- 10 ng/ml and IGF-I binding protein-1 concentration increased
significantly, as assessed by ligand and Western blot analysis. Fetal IGF-I
concentrations remained below control values throughout a subsequent
recovery period (68 +/- 12 ng/ml at 6 h). In four control fetuses and in
the ewes, plasma IGF-I concentrations were not significantly different from
control values (97 +/- 18 and 181 +/- 18 ng/ml, respectively). These data
support the hypothesis that decreases in fetal oxygen availability may
decrease fetal growth by decreasing IGF-I production and availability.
