title: Specificity of insulin-like growth factor binding to type-II IGF receptors in rabbit mammary gland and hypophysectomized rat liver.
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.
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D017451:Receptors, Somatomedin; D011994:Recombinant Proteins / Q000378:metabolism; D013002:Somatomedins / Q000378:metabolism*
chemical_list: D007328:Insulin; D017451:Receptors, Somatomedin; D011994:Recombinant Proteins; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D011972:Receptor, Insulin