Zaia A, Piantanelli L
Centre of Biochemistry, Gerontologic Research Department, INRCA, Ancona.
Boll Soc Ital Biol Sper. 1996 Mar-Apr;72(3-4):95-102.
We previously demonstrated that mouse adrenergic system undergoes age-related impairments which can be reversed by grafting thymus into old animals. Recently, our attention is devoted to brain insulin receptors (InsRs), because of their possible involvement in neuromodulation of monoaminergic systems. The paucity of information on brain InsRs in general, and on mouse in particular, prompted us to look for methods by which brain InsR characteristics can be determined accurately, before beginning a study on possible age-dependent modifications of this receptor system and their eventual recovery by thymus graft. Brain insulin receptor characteristics were studied in a group of young Balb/c-nu mice by binding competition experiments, set up incubating fresh brain membranes with a constant amount of 125I-insulin in presence of increasing concentrations of cold insulin. Experimental data were analysed using both one-site and two-site models. Comparison of results demonstrates that curvilinear Scatchard plot of brain InsRs is indicative of the presence of two binding sites with high and low affinity, respectively. Data also shows that density and affinity of the high affinity receptor subset can be determined accurately, while the low affinity receptor subpopulation presents a high degree of interindividual variability for both density and affinity. It can be concluded that this method of determination of InsR characteristics can be safely used to deepen the study of thymus graft-induced recovery of age-related modifications of brain InsR system.
我们之前证明，小鼠的肾上腺素能系统会出现与年龄相关的损伤，而将胸腺移植到老年动物体内可逆转这种损伤。最近，我们将注意力转向了脑胰岛素受体（InsRs），因为它们可能参与单胺能系统的神经调节。总体而言，关于脑InsRs的信息匮乏，尤其是关于小鼠脑InsRs的信息，这促使我们在开始研究该受体系统可能的年龄依赖性修饰及其最终通过胸腺移植恢复之前，寻找能够准确测定脑InsR特征的方法。通过结合竞争实验，对一组年轻的Balb/c-nu小鼠的脑胰岛素受体特征进行了研究，实验设置为在不断增加的冷胰岛素浓度存在的情况下，将新鲜脑膜与恒定剂量的125I-胰岛素一起孵育。使用单点和双点模型对实验数据进行了分析。结果比较表明，脑InsRs的曲线Scatchard图分别表明存在高亲和力和低亲和力的两个结合位点。数据还显示，高亲和力受体亚群的密度和亲和力可以准确测定，而低亲和力受体亚群在密度和亲和力方面均表现出高度的个体间差异。可以得出结论，这种测定InsR特征的方法可安全地用于深入研究胸腺移植诱导的脑InsR系统年龄相关修饰的恢复。
