Torlińska T, Maćkowiak P, Nogowski L, Hryniewiecki T, Witmanowski H, Perz M, M dry E, Nowak K W
Department of Physiology, University of Medical Sciences, Poznań, Poland.
J Physiol Pharmacol. 2000 Dec;51(4 Pt 2):871-81.
Aging is associated with insulin resistance but the exact molecular mechanism is still unknown. Tissue insulin resistance can be evoked by the decreased sensitivity to insulin, the decreased responsiveness to hormone or both. As the first step in insulin action is its binding to alfa subunits of the receptor we, therefore, studied the insulin binding kinetics in plasma membranes of the liver, heart and skeletal muscle in order to establish whether their ability to bind the hormone is altered with aging. Plasma membranes were prepared and purified according to Havrankowa and binding assay was performed using (125I)-iodoinsulin. The kinetic parameters of the hormone-receptor interaction were analysed by the method of Scatchard using the LIGAND-Pc v.3.1. computer program. The binding potency of insulin was calculated as IC50 using ALLFIT-Pc v.2.7. computer program. We have shown that there are striking differences in insulin binding kinetics in newborn and old rats, depending on kind of tissue tested. The liver plasma membranes ability for insulin binding, number of high (HAIR) and low (LAIR) affinity insulin receptors, values of the dissociation constants and products of association constants and number of insulin receptors, were almost the same, being not dependent on age of the rats. By contrast, there is less high affinity insulin receptors in skeletal muscle of the old animals. The most dramatic changes in insulin binding occur in the heart where both high and low affinity insulin receptors are greatly affected by aging. Our results indicate that the response of the three tissues tested to hyperglycemia and hyperinsulinemia, observed in the old rats, has not been identical and probably can be accounted for by the different distribution of insulin receptor isoforms in the liver, heart and skeletal muscles as shown recently by Vidal et al.
衰老与胰岛素抵抗相关，但确切的分子机制仍不清楚。组织胰岛素抵抗可由对胰岛素敏感性降低、对激素反应性降低或两者共同引起。由于胰岛素作用的第一步是其与受体的α亚基结合，因此，我们研究了肝脏、心脏和骨骼肌质膜中的胰岛素结合动力学，以确定它们结合激素的能力是否随衰老而改变。根据哈夫兰科娃的方法制备并纯化质膜，使用（125I）-碘胰岛素进行结合测定。采用Scatchard方法，使用LIGAND-Pc v.3.1计算机程序分析激素-受体相互作用的动力学参数。使用ALLFIT-Pc v.2.7计算机程序将胰岛素的结合效力计算为IC50。我们已经表明，新生大鼠和老年大鼠的胰岛素结合动力学存在显著差异，这取决于所测试的组织类型。肝脏质膜结合胰岛素的能力、高亲和力（HAIR）和低亲和力（LAIR）胰岛素受体的数量、解离常数的值、结合常数的乘积以及胰岛素受体的数量，几乎相同，与大鼠的年龄无关。相比之下，老年动物骨骼肌中的高亲和力胰岛素受体较少。胰岛素结合最显著的变化发生在心脏，高亲和力和低亲和力胰岛素受体都受到衰老的极大影响。我们的结果表明，在老年大鼠中观察到的所测试的三种组织对高血糖和高胰岛素血症的反应并不相同，这可能可以由维达尔等人最近所显示的肝脏、心脏和骨骼肌中胰岛素受体亚型的不同分布来解释。
