112 BIOCTIVITY OF THE EGF-I BINDING SUB-UNIT OF THE LARGE MOLECULAR WEIGHT CIRCULATING COMPLEX IN HUMAN PLASMA

Abstract

The biological activity of the partially purified insulin-like growth factor 1 [IGF-11 binding protein [BP] of the large MW circulating complex (145 K) in human plasma was evaluated using our IGF-1 Leydig (LC cell bioassay model that specifically differenciates under IGF-1 action [Bernier J. Cell.Physiol. 129:257.1986]. This BP inhibits both the 125-IG-1 binding to the specific LC IGF type 1 receptors and the dramatic increase in testosterone secretion (in response to LH) specifically induced by IGF-1. BP also inhibits the IGF-I dependent increment in LH-HCG receptor number. These BP inhibitions of IGF-I actions are specific and dose dependent. These data help to Further understand the nature of the circulating IGF-1 large MW complex and function of its IGF-1 BP.

Partial purification of the IGF-1 BP subunit included amonium sulfate precipitation. OEAE sephadex A50.S-300 sephacryl [pH-3.5] and IGF-1 affinity chromatographies then CM reverse phase HPLC. On SDS-PAGE. DEAE peak 2 (containing BP) cross-linked to I25-IGF-1 lead to two specific bands (39 K and 24 K]. This material gel filtrated (S-300. pH-7.4) lead to a 54 K complex. When cross-linking included 125-IGF-1. DEAE peak 2 and 3. SDS-PAGE lead to a major 94 K. a minor 39 K and a constant 24 K band. S-200 gel filtration then recovered a large IGF-1 MW complex, but of 125 K

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Naville, D., Chatelain, P., Ruitton, A. et al. 112 BIOCTIVITY OF THE EGF-I BINDING SUB-UNIT OF THE LARGE MOLECULAR WEIGHT CIRCULATING COMPLEX IN HUMAN PLASMA. Pediatr Res 24, 535 (1988). https://doi.org/10.1203/00006450-198810000-00133

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