Okimura Y, Kitajima N, Uchiyama T, Yagi H, Abe H, Shakutsui S, Chihara K
Division of Metabolism and Nutrition, International Center for Medical Research, Kobe, Japan.
Biochem Biophys Res Commun. 1989 Jun 15;161(2):589-95. doi: 10.1016/0006-291x(89)92640-5.
To clarify whether insulin-like growth factor I (IGF-I) is an autocrine growth factor of rat medullary thyroid carcinoma (MTC) cell line, 6-23 (clone 6), IGF-I binding to MTC cell membranes, IGF-I levels in the conditioned culture medium of MTC cells and the effects of IGF-I on methyl-[3H]thymidine incorporation to MTC cells were examined. Scatchard analysis of saturation binding studies revealed the association constant and the maximal binding capacity were 1.0 x 10(9) M-1 and 199 fmol/mg of membrane protein, respectively. The binding of [125I]IGF-I to MTC cell membranes was inhibited by unlabeled IGF-I, IGF-II and insulin; the relative potencies were IGF-I greater than IGF-II much greater than insulin, suggesting the presence of type I IGF receptors in MTC cells. IGF-I levels in the conditioned culture medium of MTC cells were 120 +/- 3 pM (mean + SE). IGF-I (10(-10) to 10(-8) M) dose-dependently stimulated methyl-[3H]thymidine incorporation to MTC cells. These findings suggest a possible role of IGF-I as an autocrine growth factor for MTC cells.
为了阐明胰岛素样生长因子I（IGF-I）是否为大鼠甲状腺髓样癌（MTC）细胞系6-23（克隆6）的自分泌生长因子，我们检测了IGF-I与MTC细胞膜的结合、MTC细胞条件培养基中的IGF-I水平以及IGF-I对MTC细胞甲基-[3H]胸腺嘧啶核苷掺入的影响。饱和结合研究的Scatchard分析显示，结合常数和最大结合容量分别为1.0×10⁹ M⁻¹和199 fmol/mg膜蛋白。未标记的IGF-I、IGF-II和胰岛素可抑制[¹²⁵I]IGF-I与MTC细胞膜的结合；相对效力为IGF-I＞IGF-II＞＞胰岛素，提示MTC细胞中存在I型IGF受体。MTC细胞条件培养基中的IGF-I水平为120±3 pM（平均值+标准误）。IGF-I（10⁻¹⁰至10⁻⁸ M）剂量依赖性地刺激MTC细胞甲基-[3H]胸腺嘧啶核苷掺入。这些发现提示IGF-I可能作为MTC细胞的自分泌生长因子发挥作用。
