Journal of Clinical Endocrinology & Metabolism, Vol 65, 423-431, Copyright © 1987 by Endocrine Society

ARTICLES

Two immunoreactive binding proteins for insulin-like growth factors in human amniotic fluid: relationship to fetal maturity

RC Baxter, JL Martin and MH Wood

A binding protein for insulin-like growth factors (IGFs) has been purified from human amniotic fluid by IGF-I affinity chromatography and high performance reverse phase chromatography. This protein, with an apparent molecular mass of 28K nonreduced and 34K reduced, had an identical amino-terminus to a previously purified binding protein from amniotic fluid and to placental protein 12. The purified preparation (BP-28) bound both IGFs with high affinity [Ka, 6.55 +/- 2.24 (+/- SD) L/nmol for IGF-I and 3.23 +/- 1.05 L/nmol for IGF-II], with approximately 0.5 mol binding sites/mol BP-28 for either ligand. A 53K IGF-binding protein purified from human plasma (BP-53) did not cross- react in a RIA for BP-28, and BP-28 had less than 0.1% molar cross- reactivity in a RIA for BP-53. Human amniotic fluid reacted strongly in both assays. Fractionation of amniotic fluid samples by reverse phase chromatography showed that BP-28 and BP-53 immunoreactivities were present on separate proteins. In 40 third trimester amniotic fluid samples selected to cover a wide range of lecithin to sphingomyelin ratios, the mean concentrations of BP-28 and BP-53 were 37.6 +/- 17.6 (+/- SD) and 4.6 +/- 1.6 mg/L, respectively. Significant negative correlations were found between the levels of both BP-28 and BP-53 and the lecithin to sphingomyelin ratio, suggesting an association between the levels of both proteins and the degree of fetal maturity. A significant positive association was also found between the levels of BP-28 and BP-53. We conclude that the 28K IGF-binding protein from amniotic fluid, like the previously purified 53K binding protein, has high affinity for both IGF-I and IGF-II, that it coexists in amniotic fluid with BP-53 or a related protein, and that the levels of both proteins decline with increasing fetal maturity.

This article has been cited by other articles:

				V. E. Murphy, R. Smith, W. B. Giles, and V. L. Clifton Endocrine Regulation of Human Fetal Growth: The Role of the Mother, Placenta, and Fetus Endocr. Rev., April 1, 2006; 27(2): 141 - 169. [Abstract] [Full Text] [PDF]

				C. S. Watson, P. Bialek, M. Anzo, J. Khosravi, S.-P. Yee, and V. K. M. Han Elevated Circulating Insulin-Like Growth Factor Binding Protein-1 Is Sufficient to Cause Fetal Growth Restriction Endocrinology, March 1, 2006; 147(3): 1175 - 1186. [Abstract] [Full Text] [PDF]

				S. S. Y. Chan, S. M. Twigg, S. M. Firth, and R. C. Baxter Insulin-Like Growth Factor Binding Protein-3 Leads to Insulin Resistance in Adipocytes J. Clin. Endocrinol. Metab., December 1, 2005; 90(12): 6588 - 6595. [Abstract] [Full Text] [PDF]

				J. C Brand-Miller, V. Liu, P. Petocz, and R. C Baxter The glycemic index of foods influences postprandial insulin-like growth factor-binding protein responses in lean young subjects Am. J. Clinical Nutrition, August 1, 2005; 82(2): 350 - 354. [Abstract] [Full Text] [PDF]

				G. Blanchard, P. Nguyen, C. Gayet, I. Leriche, B. Siliart, and B.-M. Paragon Rapid Weight Loss with a High-Protein Low-Energy Diet Allows the Recovery of Ideal Body Composition and Insulin Sensitivity in Obese Dogs J. Nutr., August 1, 2004; 134(8): 2148S - 2150S. [Full Text] [PDF]

				D. Mesotten, P. J. D. Delhanty, F. Vanderhoydonc, K. V. Hardman, F. Weekers, R. C. Baxter, and G. van den Berghe Regulation of Insulin-Like Growth Factor Binding Protein-1 during Protracted Critical Illness J. Clin. Endocrinol. Metab., December 1, 2002; 87(12): 5516 - 5523. [Abstract] [Full Text] [PDF]

				D. B. O'Gorman, J. Weiss, A. Hettiaratchi, S. M. Firth, and C. D. Scott Insulin-Like Growth Factor-II/Mannose 6-Phosphate Receptor Overexpression Reduces Growth of Choriocarcinoma Cells in Vitro and in Vivo Endocrinology, November 1, 2002; 143(11): 4287 - 4294. [Abstract] [Full Text] [PDF]

				G. Van den Berghe, F. Weekers, R. C. Baxter, P. Wouters, A. Iranmanesh, R. Bouillon, and J. D. Veldhuis Five-Day Pulsatile Gonadotropin-Releasing Hormone Administration Unveils Combined Hypothalamic-Pituitary-Gonadal Defects Underlying Profound Hypoandrogenism in Men with Prolonged Critical Illness J. Clin. Endocrinol. Metab., July 1, 2001; 86(7): 3217 - 3226. [Abstract] [Full Text] [PDF]

				J. D. Wallace, R. C. Cuneo, R. Baxter, H. Orskov, N. Keay, C. Pentecost, R. Dall, T. Rosen, J. O. Jorgensen, A. Cittadini, et al. Responses of the Growth Hormone (GH) and Insulin-Like Growth Factor Axis to Exercise, GH Administration, and GH Withdrawal in Trained Adult Males: A Potential Test for GH Abuse in Sport J. Clin. Endocrinol. Metab., October 1, 1999; 84(10): 3591 - 3601. [Abstract] [Full Text] [PDF]

				S. R. Edmondson, V. C. Russo, A. C. McFarlane, C. J. Wraight, and G. A. Werther Interactions between Growth Hormone, Insulin-Like Growth Factor I, and Basic Fibroblast Growth Factor in Melanocyte Growth J. Clin. Endocrinol. Metab., May 1, 1999; 84(5): 1638 - 1644. [Abstract] [Full Text]

				G. Van den Berghe, P. Wouters, F. Weekers, S. Mohan, R. C. Baxter, J. D. Veldhuis, C. Y. Bowers, and R. Bouillon Reactivation of Pituitary Hormone Release and Metabolic Improvement by Infusion of Growth Hormone-Releasing Peptide and Thyrotropin-Releasing Hormone in Patients with Protracted Critical Illness J. Clin. Endocrinol. Metab., April 1, 1999; 84(4): 1311 - 1323. [Abstract] [Full Text]

				L. J. Schedlich, T. F. Young, S. M. Firth, and R. C. Baxter Insulin-like Growth Factor-binding Protein (IGFBP)-3 and IGFBP-5 Share a Common Nuclear Transport Pathway in T47D Human Breast Carcinoma Cells J. Biol. Chem., July 17, 1998; 273(29): 18347 - 18352. [Abstract] [Full Text] [PDF]

				S. M. Twigg and R. C. Baxter Insulin-like Growth Factor (IGF)-binding Protein 5 Forms an Alternative Ternary Complex with IGFs and the Acid-labile Subunit J. Biol. Chem., March 13, 1998; 273(11): 6074 - 6079. [Abstract] [Full Text] [PDF]

				L. J. Schedlich, S. L. Le Page, S. M. Firth, L. J. Briggs, D. A. Jans, and R. C. Baxter Nuclear Import of Insulin-like Growth Factor-binding Protein-3 and -5 Is Mediated by the Importin beta Subunit J. Biol. Chem., July 28, 2000; 275(31): 23462 - 23470. [Abstract] [Full Text] [PDF]