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Fetal Sheep Serum Contains a High Molecular Weight Insulin-Like Growth Factor (IGF) Binding Protein that Is Acid Stable and Specific for IGF-II

Fetal Sheep Serum Contains a High Molecular Weight Insulin-Like Growth Factor (IGF) Binding... Abstract We have used radiolabeled ovine insulin-like growth factor II (oIGF-II) and human IGF-I (hIGF-I) to investigate the nature of the IGF binding proteins in fetal sheep serum. Incubation of fetal sheep serum with [125I]oIGF-II, followed by chromatography on Fractogel TSK HW55(S), revealed the presence of two major binding protein species, a lower molecular weight binding protein (apparent mol wt - 60,000) and a much higher molecular weight binding protein (apparent mol wt - 500,000). Only the lower molecular weight binding protein complex was seen in serum from adult nonpregnant sheep. The lower molecular weight binding protein in fetal and adult sheep serum bound both [125I]oIGF-II and [125I]hIGF-I, both of which could be displaced by unlabeled oIGF-II or hIGF-I. However, the very high molecular weight binding protein bound only [125I]oIGF-II, and this could only be displaced by unlabeled oIGF-II. The very high molecular weight binding protein appears to bind approximately 40% of the endogenous oIGF-II. We have purified the very high molecular weight binding protein from fetal sheep serum using anion exchange, Concanavalin A Sepharose, and hydrophobic interaction chromatography. The purified binding protein preparation did not contain any lower molecular weight binding protein and did not bind [125I]hIGF-I. In addition, this binding protein was stable at pH 3.2 for 1 h. Thus, fetal sheep serum contains a very high molecular weight IGF binding glycoprotein that is acid stable and specific for IGF-II. (Endocrinology121: 1975–1984, 1987) This content is only available as a PDF. Author notes * This work was supported by a program grant from the National Health and Medical Research Council of Australia (to G.D.T.). Copyright © 1987 by The Endocrine Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Endocrinology Oxford University Press

Fetal Sheep Serum Contains a High Molecular Weight Insulin-Like Growth Factor (IGF) Binding Protein that Is Acid Stable and Specific for IGF-II

HEY, A., W.; BROWNE, C., A.; THORBURN, G., D.
Endocrinology , Volume 121 (6) – Dec 1, 1987
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References (25)

Publisher
Oxford University Press
Copyright
Copyright © 1987 by The Endocrine Society
ISSN
0013-7227
eISSN
1945-7170
DOI
10.1210/endo-121-6-1975
Publisher site
See Article on Publisher Site

Abstract

Abstract We have used radiolabeled ovine insulin-like growth factor II (oIGF-II) and human IGF-I (hIGF-I) to investigate the nature of the IGF binding proteins in fetal sheep serum. Incubation of fetal sheep serum with [125I]oIGF-II, followed by chromatography on Fractogel TSK HW55(S), revealed the presence of two major binding protein species, a lower molecular weight binding protein (apparent mol wt - 60,000) and a much higher molecular weight binding protein (apparent mol wt - 500,000). Only the lower molecular weight binding protein complex was seen in serum from adult nonpregnant sheep. The lower molecular weight binding protein in fetal and adult sheep serum bound both [125I]oIGF-II and [125I]hIGF-I, both of which could be displaced by unlabeled oIGF-II or hIGF-I. However, the very high molecular weight binding protein bound only [125I]oIGF-II, and this could only be displaced by unlabeled oIGF-II. The very high molecular weight binding protein appears to bind approximately 40% of the endogenous oIGF-II. We have purified the very high molecular weight binding protein from fetal sheep serum using anion exchange, Concanavalin A Sepharose, and hydrophobic interaction chromatography. The purified binding protein preparation did not contain any lower molecular weight binding protein and did not bind [125I]hIGF-I. In addition, this binding protein was stable at pH 3.2 for 1 h. Thus, fetal sheep serum contains a very high molecular weight IGF binding glycoprotein that is acid stable and specific for IGF-II. (Endocrinology121: 1975–1984, 1987) This content is only available as a PDF. Author notes * This work was supported by a program grant from the National Health and Medical Research Council of Australia (to G.D.T.). Copyright © 1987 by The Endocrine Society

Journal

Endocrinology – Oxford University Press

Published: Dec 1, 1987

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