Penhoat A, Chatelain P G, Jaillard C, Saez J M
INSERM U 307, Hôpital Debrousse, Lyon, France.
Endocrinology. 1988 Jun;122(6):2518-26. doi: 10.1210/endo-122-6-2518.
We have characterized insulin-like growth factor I (IGF-I) and insulin receptors in cultured bovine adrenal cells by binding and cross-linking affinity experiments. At equilibrium the dissociation constant and the number of binding sites per cell for IGF-I were 1.4 +/- (SE) 0.3 x 10(-9) M and 19,200 +/- 2,100, respectively. Under reduction conditions, disuccinimidyl suberate cross-linked [125I]iodo-IGF-I to one receptor complex with an Mr of 125,000. Adrenal cells also contain specific insulin receptors with an apparent dissociation constant (Kd) of 10(-9) M. Under reduction conditions [125I]iodo-insulin binds to one band with an approximate Mr of 125,000. IGF-I and insulin at micromolar concentrations, but not at nanomolar concentrations, slightly stimulated DNA synthesis, but markedly potentiated the mitogenic action of fibroblast growth factor. Adrenal cells cultured in a serum-free medium containing transferrin, ascorbic acid, and insulin (5 micrograms/ml) maintained fairly constant angiotensin-II (A-II) receptor concentration per cell and increased cAMP release on response to ACTH and their steroidogenic response to both ACTH and A-II. When the cells were cultured in the same medium without insulin, the number of A-II receptors significantly decreased to 65% and the increased responsiveness was blunted. Treatment of such cells for 3 days with increasing concentrations of IGF-I (1-100 ng/ml) produced a 2- to 3-fold increase in A-II receptors and enhanced the cAMP response (3- to 4-fold) to ACTH and the steroidogenic response (4- to 6-fold) to ACTH and A-II. These effects were time and dose dependent (ED50 approximately equal to 10(-9) M). Insulin at micromolar concentrations produced an effect similar to that of IGF-I, but at nanomolar concentrations the effect was far less. The enhanced steroidogenic responsiveness of IGF-I and insulin-treated cells were related to an enhanced capacity to produce pregnenolone and an increased activity of several steroid hydroxylases. These results indicate that both IGF-I and insulin, acting through their own receptor, play an important role in the maintenance of specific adrenal cell functions. However, at physiological concentrations IGF-I is more potent than insulin.
我们通过结合和交联亲和实验，对培养的牛肾上腺细胞中的胰岛素样生长因子I（IGF-I）和胰岛素受体进行了表征。在平衡状态下，IGF-I的解离常数和每个细胞的结合位点数分别为1.4±（标准误）0.3×10⁻⁹ M和19,200±2,100。在还原条件下，辛二酸二琥珀酰亚胺酯将[¹²⁵I]碘-IGF-I交联到一个分子量为125,000的受体复合物上。肾上腺细胞还含有特异性胰岛素受体，其表观解离常数（Kd）为10⁻⁹ M。在还原条件下，[¹²⁵I]碘胰岛素与一条分子量约为125,000的条带结合。微摩尔浓度而非纳摩尔浓度的IGF-I和胰岛素可轻微刺激DNA合成，但能显著增强成纤维细胞生长因子的促有丝分裂作用。在含有转铁蛋白、抗坏血酸和胰岛素（5微克/毫升）的无血清培养基中培养的肾上腺细胞，每个细胞的血管紧张素-II（A-II）受体浓度保持相当恒定，并在对促肾上腺皮质激素（ACTH）的反应中增加环磷酸腺苷（cAMP）释放，以及对ACTH和A-II的类固醇生成反应增强。当细胞在不含胰岛素的相同培养基中培养时，A-II受体数量显著减少至65%，反应性增强减弱。用浓度递增的IGF-I（1 - 100纳克/毫升）处理此类细胞3天，可使A-II受体增加2至3倍，并增强对ACTH的cAMP反应（3至4倍）以及对ACTH和A-II的类固醇生成反应（4至6倍）。这些效应具有时间和剂量依赖性（半数有效剂量约等于10⁻⁹ M）。微摩尔浓度的胰岛素产生的效应与IGF-I相似，但纳摩尔浓度时效应则小得多。IGF-I和胰岛素处理细胞增强的类固醇生成反应性与孕烯醇酮生成能力增强以及几种类固醇羟化酶活性增加有关。这些结果表明，IGF-I和胰岛素均通过自身受体发挥作用，在维持特定肾上腺细胞功能中起重要作用。然而，在生理浓度下，IGF-I比胰岛素更有效。
