Specificity of insulin-like growth factor binding to type-II IGF receptors in rabbit mammary gland and hypophysectomized rat liver.
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.
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*
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