【产品名称】
通用名称:胰岛素生长因子I检测试剂盒(酶联免疫法)
英文名称:IGF-I ELISA
【包装规格】96人份/盒
【样本类型】血清、血浆
【预期用途】
用于定量测定人血清和血浆中人胰岛素样生长因子I(IGF-I),仅供科研使用。
【背景知识】
胰岛素样生长因子(IGF)H和-在许多细胞类型的增殖、分化和特定功能的调节中发挥关键作用(1-3)。IGF-/与somatomedin c (Sm-C)相同(4)分子量为7649道尔顿(5).它的主要调节剂是生长激素(GH)和营养(6),尽管它在特定组织中的合成受多种热带激素和其他肽生长因子的影响。与许多其他肽激素相比,IGF以高亲和力与特异性结合蛋白(IGFBP)结合。目前已知有七类结合蛋白(7,8,22)。它们要么以相似的亲和力结合IGF-I和IGF-II,要么表现出对IGF-II的偏好(9.10)。测量IGF-I的一个主要问题是在测定中干扰iGFBPs。在未经处理的血清样品中直接测定(11)会导致不正确的结果,因为由于在测定孵育期间IGF-IGFBP-3复合物的解离极慢,因此只有部分IGF-1可用于测量。根据样品中IGF与IGFBP的比例,会发生干扰:(参见图1中的示例)
因此,人们开发了多种方法在实际测量前将IGF-I从其结合蛋白中分离出来:(a)酸性条件下的尺寸排阻色谱法,(b)固相萃取和(c)酸-醇萃取(2,12,13))。然而,这些方法要么费时费力,要么导致不完全,尤其是不可重现的回收。最普遍的方法是酸-醇萃取(13,14)。然而,由于共沉淀,它仅产生70-80%的结合IGF-。因此,在这样的提取步骤之后测量的绝对值非常低(15)。提取过程导致样品的预稀释,从而降低了测定的灵敏度。此外,提取仅不足以去除IGFBP。提取物中残留的IGFBP仍会干扰检测。除血清或血浆外,酸-酒精提取在其他样品(例如细胞培养基)中完全无效。正是在这里,IGF-1的测定特别困难,因为这些样品通常含有大量过量的IGFBP。
【临床意义】
除了GH,还有许多因素影响血清IGF-水平。在营养不良/吸收不良、甲状腺功能减退、肝病、未经治疗的糖尿病、慢性炎症性疾病(1,6)、恶性肿瘤或多发性创伤中发现水平降低。高水平可在性早熟或肥胖中发现的。对于IGF-I测定的正确解释至关重要的是要考虑IGF-水平的年龄依赖性(年龄依赖性参考值见表2和图4-6) .
由于其GH依赖性,血清IGF-1的测定对于诊断生长障碍具有重要价值,特别是对于GH缺乏或肢端肥大症(6,16-19,23,24)。与GH测定相比,IGF-J测定最重要的优点是其稳定的昼夜浓度,即一次测量就足以提供信息。因此,IGF-1测定应成为实验室诊断的重中之重。显然,正常水平排除了GH-IGF-1轴的紊乱。低水平,即接近或低于与年龄相关的第5个百分位的水平,需要进一步的诊断步骤。如果排除其他导致低血清IGF-I的原因(如营养不良或肝功能受损),则IGF-I水平低于正常水平可能是GH分泌受损的迹象。区分健康、身材矮小、非GH缺乏的儿童和患有"经典的"生长激素缺乏症",已发现0.1个百分位数是一个很好的分界点,尤其是从8岁开始。然而,必须注意的是,没有生长激素缺乏症的身材矮小儿童的分数很可能在0.1和5个百分位数之间(19)相比之下,肢端肥大症的特征是病理性升高的IGF-I水平,这似乎比GH测量值更能反映疾病严重程度(17,18,20)。
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