Insulin-like growth factor-binding proteins in the human fetus: tissue-specific protein secretion, immunologic characterization, and gene expression.
OBJECTIVE
The objectives of this study were to investigate the profile of insulin-like growth factor-binding proteins secreted by human fetal tissues and their immunologic identification and tissue-specific gene expression.


METHODS
Explants of midgestational fetal tissues from seven fetuses were cultured with and without cycloheximide. Conditioned media were examined for insulin-like growth factor-binding proteins by Western ligand blot analysis, and insulin-like growth factor-binding proteins were identified by immunoprecipitation. Gene expression was analyzed by Northern analysis.


RESULTS
Fetal liver and kidney explants secreted insulin-like growth factor-binding protein-1 to insulin-like growth factor-binding protein-4, with insulin-like growth factor-binding protein-1 being the most prominent in liver. Fetal lung secreted insulin-like growth factor-binding protein-2 and insulin-like growth factor-binding protein-4 and lesser amounts of insulin-like growth factor-binding protein-3, whereas white matter explants secreted exclusively insulin-like growth factor-binding protein-2 and insulin-like growth factor-binding protein-4. Cycloheximide inhibited secretion of binding proteins, suggesting de novo synthesis. Northern blot analyses were consistent with the protein studies.


CONCLUSIONS
These data demonstrate that insulin-like growth factor-binding protein secretion by fetal tissues is tissue specific.
Pannier
E M
EM
Department of Gynecology and Obstetrics, Stanford University Medical Center, CA 94305-5317.
Irwin
J C
JC
Giudice
L C
LC
D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D005333:Fetus / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007668:Kidney / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D011233:Precipitin Tests
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D003513:Cycloheximide