ROLE OF ALTERED MEMBRANE FUNCTION IN XENOBIOTIC TOXICITY

膜功能改变在异生物毒性中的作用

• 批准号: 6162302
• 负责人: J B PRITCHARD
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6162302
• 关键词: active transport; alpha ketoglutarate; bioenergetics; blood brain barrier; cell membrane; cytoplasm; drug /agent; intracellular; ion transport; laboratory rat; membrane transport proteins; microtubules; mitochondria; renal tubular transport; secretion; tissue /cell culture; toxicology; toxin; vesicle /vacuole

Summary of Work: Renal secretory transport of organic anions (OA) and organic cations (OC) controls the excretion of most foreign chemicals and/or their metabolites. We have previously characterized the mechanisms and energetics of both processes. Our current focus is the biochemistry of these transport proteins; their development, expression, and control; and their impact on the toxicity of xenobiotics. We have begun to identify the genes coding for these transport proteins using expression cloning in Xenopus oocytes. Because of their large size and ability to make efficient use of foreign mRNA, it is relatively easy to inject mRNA and assay for expressed transport activity in each egg. We have now cloned one of the OC transport proteins and one OA transporter as well. The cloned OC carrier (OCT2) has been fully sequenced and is distinct from the other recently cloned OC transporter (OCT1). OCT1 has been tentatively identified as the basolateral OC carrier. Functional data indicates that OCT2 shares many features with the luminal OC/proton exchanger, including proton-dependent transport as well as similar substrate specificity and kinetic constants. However, it can also mediate potential driven OC transport, a property of the basolateral carrier. Studies using monolayer cultures of transfected epithelial cells have been initiated to resolve this issue. The cloned OA transport protein has also been sequenced. Functional studies demonstrate that it is basolateral OA/ -ketoglutarate exchanger which mediates uphill entry of OA into the tubular cells. It is the first renal organic anion transporter to be cloned and has been designated as ROAT1. It's properties include a Km of about 100 muM, inhibition by a variety of OAs but not OCs, cis-inhibition and trans-stimulation by -ketoglutarate, and independence of membrane potential -- all properties of the basolateral OA carrier. A related study assessed the renal mechanisms which might contribute to the observation that phenolphthalein causes renal tumors. These studies, in both isolated membrane vesicles and intact tubules, demonstrated rapid and effective renal uptake of the parent molecule and its glucuronide conjugate via the OA system; thus, apparently rendering the kidney particularly at risk for the toxic effects of these compounds. In addition, both parent and metabolite were potent inhibitors of renal elimination of other anionic xenobiotics.

工作摘要：有机阴离子（OA）和 有机阳离子（OC）控制大多数外国化学物质的排泄 和/或他们的代谢物。 我们以前已经表征了 这两个过程的机制和能量学。 我们目前的重点是 这些转运蛋白的生物化学；他们的发展，表达， 和控制；以及它们对异生元毒性的影响。 我们有 开始使用使用这些传输蛋白编码的基因 异武卵母细胞中的表达克隆。 由于它们的大小和 有效利用外国mRNA的能力，相对容易 注入mRNA和测定每个卵中表达的运输活性。 我们 现在将一种OC转运蛋白和一个OA转运蛋白克隆 也是如此。克隆的OC载体（OCT2）已完全测序，为 与其他最近克隆的OC转运蛋白不同（OCT1）。 Oct1具有 被暂时识别为基底外侧OC载体。 功能 数据表明OCT2与Luminal OC/Proton共享许多功能 交换器，包括质子依赖的运输以及类似 底物特异性和动力学常数。 但是，它也可以 调解潜在驱动的OC运输，这是基底外侧的特性 载体。 使用转染上皮的单层培养物的研究 已经启动细胞来解决此问题。 克隆的OA运输 蛋白也已被测序。 功能研究表明 是基底外侧OA/ -Ketoglutarate交换器，可介导上坡进入 OA进入管状细胞。 这是第一个肾脏有机阴离子 转运蛋白要克隆并已被指定为ROAT1。 它是 特性包括大约100个妈妈的公里，多种OA的抑制作用 但不是OCS，-Ketoglutarate的CIS抑制和反式刺激，以及 膜电位的独立性 - 基底外侧的所有特性 OA载体。 一项相关研究评估了可能 有助于观察到苯酚会导致肾脏肿瘤。 这些研究在分离的膜囊泡和完整的小管中， 表现出父母分子的快速有效的肾脏摄取 其通过OA系统结合葡萄糖醛酸酯；因此，显然是渲染 肾脏尤其有可能产生这些化合物的毒性作用的风险。 另外，母体和代谢物都是肾脏的有效抑制剂 消除其他阴离子异生元。