Specificity of insulin-like growth factor binding to type-II IGF receptors in rabbit mammary gland and hypophysectomized rat liver |
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Authors: | B Barenton H J Guyda C G Goodyer C Polychronakos B I Posner |
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Institution: | INRA-ENSA, Station de Physiologie Animale, Montpellier, France. |
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Abstract: | We have reevaluated IGF binding specificity to membrane receptors in rabbit mammary gland (RMG) and hypophysectomized rat liver (HRL) using recombinant DNA-derived and synthetic analogues of human IGF-I and highly purified IGF-II. SDS-PAGE demonstrated that 125I]IGF-I bound to type-I IGF receptors in RMG; this binding was inhibited in a similar fashion by the IGF-I analogues (IC50 = 10 ng/ml) and to a lesser extent by IGF-II (IC50 = 60 ng/ml). 125I]IGF-II bound to type-II IGF receptors in both RMG and HRL. The IC50 for IGF-II was 9 and 3 ng/ml with RMG and HRL, respectively. At a dose as high as 1 microgram/ml, IGF-I analogues inhibited less than 20% of 125I]IGF-II binding. These results suggest that IGF-I has little or no affinity for type-II IGF receptors. |
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