Abstract
Insulin-like growth factors (IGFs) are known to be carried in the blood by specific binding proteins (BPs) with which they form two complexes of apparent mol. wt. > 100 K ("big" complex) and 40-60 K ("little" complex). The former appears to be GH-dependent and consists of at least two subunits, one acid-stable which binds IGFs and the other acid-labile. To characterize the BPs after separation of the two complexes by gel filtration at pH 7.4, our approach has been to combine electroblotting with SDS-PAGE. With this technigue the BPs are dissociated from their complexes and the free forms, tranferred on a nylon membrane, are detected by autoradiography after incubation with [125I] IGF I. In the normal serum, two main bands (∼ 38 and 42 K) were found both in the big and the little complex. Three extra fainter bands (∼ 23, 28 and 34 K) were found in the latter. Similar pattern was obtained with hypopituitary serum although the proportion of the faster forms (∼ 28 and 34 K) seemed to be increased. Binding material of mol. wt. > 100 K was also found in the big complex, only in the normal serum. All the bands were specific as shown with an excess of cold IGF.
Conclusion: 1) The IGF BPs appear to be heterogenous. 2) Two main forms are found identical in the two complexes 3) The ratio of the various forms is different in the normal and the hypopituitary serum.
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Hardouin, S., Hossenlopp, P., Van Gennip, L. et al. 54 STRUCTURAL SIMILARITIES AND DIFFERENCES AMONG THE IGF BINDING PROTEINS PRESENT IN THE TWO MACROMOLECULAR FORMS OF SERUM [IGF-BP] COMPLEXES. Pediatr Res 19, 612 (1985). https://doi.org/10.1203/00006450-198506000-00074
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DOI: https://doi.org/10.1203/00006450-198506000-00074