Milton M N, Elcombe C R, Kass G E, Gibson G G
University of Surrey, Department of Biochemistry, Guildford, U.K.
Biochem Pharmacol. 1988 Mar 1;37(5):793-8. doi: 10.1016/0006-2952(88)90163-3.
The existence of a postulated hepatic receptor responsible for the peroxisomal proliferation induced in rodents by hypolipidaemic drugs has been investigated. [3H]-nafenopin and [3H]-ciprofibrate were used as labelled ligands and two competitive binding assays, using either a charcoal-dextran or a hydroxylapatite method, were developed to investigate potential binding. In both assay systems, specific displaceable binding of either nafenopin or ciprofibrate to whole homogenate, microsomal and cytosolic fractions of rat liver could not be detected in a variety of buffer systems. A positive control of ligand binding to bovine serum albumin indicated the validity of the binding assays used. In addition, both nafenopin and ciprofibrate exhibited displaceable binding to serum albumin using the hydroxylapatite binding assay and a Scatchard analysis of the binding of [3H]-nafenopin to fatty acid free rat serum albumin yielded a dissociation constant of 5.2 x 10(-7) M and 86 pmol of ligand bound per mg protein. Taken collectively, our data strongly argues against the existence of a specific hepatic peroxisome proliferation receptor and indicates that the peroxisome proliferating hypolipidaemic drugs bind to serum albumin and possibly to other cellular proteins not involved in the activation of genes necessary for peroxisome proliferation.
对一种假定的肝脏受体的存在进行了研究，该受体负责降血脂药物在啮齿动物中诱导的过氧化物酶体增殖。[3H] - 萘酚平及[3H] - 环丙贝特被用作标记配体，并开发了两种竞争性结合试验，分别采用活性炭 - 葡聚糖法或羟基磷灰石法来研究潜在的结合情况。在这两种试验系统中，在多种缓冲体系下，均未检测到萘酚平或环丙贝特与大鼠肝脏全匀浆、微粒体及胞质部分的特异性可置换结合。配体与牛血清白蛋白结合的阳性对照表明所采用结合试验的有效性。此外，采用羟基磷灰石结合试验时，萘酚平和环丙贝特均表现出与血清白蛋白的可置换结合，并且对[3H] - 萘酚平与无脂肪酸大鼠血清白蛋白结合的Scatchard分析得出解离常数为5.2×10(-7)M，每毫克蛋白质结合86皮摩尔配体。总体而言，我们的数据有力地反驳了特异性肝脏过氧化物酶体增殖受体的存在，并表明过氧化物酶体增殖性降血脂药物与血清白蛋白结合，可能还与其他不参与过氧化物酶体增殖所需基因激活的细胞蛋白结合。
