Rechler M M, Zapf J, Nissley S P, Froesch E R, Moses A C, Podskalny J M, Schilling E E, Humbel R E
Endocrinology. 1980 Nov;107(5):1451-9. doi: 10.1210/endo-107-5-1451.
Insulin-like growth factors (IGFs) I and II, purified from human plasma, and multiplication-stimulating activity (MSA), purified from media conditioned by the BRL 3A rat liver cell line, are polypeptides with similar biological and biochemical properties. We have compared the interaction of 125I-labeled and unlabeled MSA, IGF-I, and IGF-II with four intact cell or cell membrane preparations previously shown to possess MSA receptors: rat liver plasma membranes, chick embryo fibroblasts, human fibroblasts, and BRL 3A2 cells. In each case, specific binding of 125I-labeled IGF-I and IGF-II was demonstrated. With each 125I-labeled peptide, significant inhibition of binding and parallel dose-response curves were observed with unlabeled IGF-I, IGF-II, and MSA. Striking differences were noted, however, in the relative potencies of the unlabeled peptides as competitive inhibitors of binding. We conclude that the different specificities of binding inhibition reflect a significant heterogeneity among IGF receptors. A similar heterogeneity appears to occur among somatomedin carrier proteins in rat and human sera.
从人血浆中纯化得到的胰岛素样生长因子（IGFs）Ⅰ和Ⅱ，以及从BRL 3A大鼠肝细胞系条件培养基中纯化得到的促增殖活性因子（MSA），都是具有相似生物学和生化特性的多肽。我们比较了125I标记和未标记的MSA、IGF-Ⅰ和IGF-Ⅱ与四种完整细胞或细胞膜制剂的相互作用，这些制剂先前已被证明具有MSA受体：大鼠肝细胞膜、鸡胚成纤维细胞、人成纤维细胞和BRL 3A2细胞。在每种情况下，均证明了125I标记的IGF-Ⅰ和IGF-Ⅱ的特异性结合。对于每种125I标记的肽，未标记的IGF-Ⅰ、IGF-Ⅱ和MSA均观察到结合的显著抑制和平行的剂量反应曲线。然而，在未标记肽作为结合竞争性抑制剂的相对效力方面，发现了显著差异。我们得出结论，结合抑制的不同特异性反映了IGF受体之间存在显著的异质性。大鼠和人血清中的生长调节素载体蛋白之间似乎也存在类似的异质性。
