This Article Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints, Permissions and Rights Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by D'ERCOLE, A. J. Articles by KORTLEVE, D. J. Search for Related Content PubMed PubMed Citation Articles by D'ERCOLE, A. J. Articles by KORTLEVE, D. J.

Somatomedin-C/Insulin-Like Growth Factor I-Binding Proteins in Human Amniotic Fluid and in Fetal and Postnatal Blood: Evidence of Immunological Homology^*

A. JOSEPH D'ERCOLE, STENVERT L. S. DROP and DICKY J. KORTLEVE

Departments of Pediatrics, University of North Carolina School of Medicine Chapel Hill, North Carolina 27514
and Erasmus University and University Hospital/Sophia Children's Center Rotterdam, The Netherlands

Address all correspondence and requests for reprints to: A. Joseph D'Ercole, M.D., Department of Pediatrics, 509 Clinical Sciences Building 229H, University of North Carolina, Chapel Hill, North Carolina 27514.

By using the chemical cross-linking agent dissuccinimidyl suberate and [¹²⁵I]somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) to affinity label Sm-binding proteins, we identified a 30,000- to 40,000-dalton (30-40K) [¹²⁵I] Sm-C-binding protein complex in midterm amniotic fluid and cord blood. An antibody raised against a Sm-binding protein purified from midterm amniotic fluid recognized this labeled complex not only in amniotic fluid but also in fetal serum and term cord and several postnatal human plasmas, indicating that the 30-40K Sm-binding proteins in each are similar or identical. The binding proteins in amniotic fluid appear to possess binding sites specific for Sm-C, because under the conditions employed, unlabeled Sm-C was at least 10-fold more potent than IGF-II or multiplication-stimulating activity in competing with [¹²⁵I]Sm-C for binding. Although [^125I]IGF-II could be cross-linked to similarly sized proteins, unlabeled Sm-C also competed for this binding better than either unlabeled IGF-II or MSA (at least 5-fold greater potency). These findings suggest that this amniotic fluid Sm-binding protein is primarily a carrier of Sm-C, but does not exclude the possibility that a binding site or a distinct binding protein exists which is specific for IGF-II but not amenable to cross-linking by the procedure used. Because unlabeled Sm-C was less potent in inhibiting the binding of [¹²⁵]Sm-C to amniotic fluid than to cord plasma proteins, the amniotic fluid binding protein is either more abundant or less avidly binds [¹²⁵I]Sm-C than the cord plasma binding protein. (J Clin EndocrinolMetab 61: 612,1985)

^* Presented in part at the Seventh International Congress of Endocrinology, Quebec City, Quebec, Canada, 1984. This work was supported by a NICHHD grant (HD-08299), a March of Dimes Basic Research Grant (1–758), the Sophia Foundation for Medical Research, and Nordisk Grant for the Study of Growth.

Recipient of USPHS Research Career Development Award HD-00435.

Received February 15, 1985.

This article has been cited by other articles:

				M. J. Khosravi, A. Diamandi, J. Mistry, R. G. Krishna, and A. Khare Acid-Labile Subunit of Human Insulin-Like Growth Factor-Binding Protein Complex: Measurement, Molecular, and Clinical Evaluation J. Clin. Endocrinol. Metab., December 1, 1997; 82(12): 3944 - 3951. [Abstract] [Full Text] [PDF]