CELLULAR MECHANISMS OF XENOBIOTIC TRANSPORT

异生物运输的细胞机制

• 批准号: 3841164
• 负责人: D S MILLER
• 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/3841164
• 关键词: animal tissue; anions; bioenergetics; biological models; cations; cytoplasm; diffusion; fluorescence microscopy; ion transport; kidney cell; membrane permeability; microinjections; organic chemicals; renal tubular transport; renal tubule; tissue /cell culture; toxin metabolism; vesicle /vacuole; video recording system

An important function of the vertebrate kidney is the excretion of potentially toxic chemicals, such as waste products of cellular metabolism, xenobiotics and xenobiotic metabolites. This occurs primarily in the proximal tubule, where renal transport systems remove organic anions and organic cations from peritubular capillaries and transport them across the tubular epithelium into the lumen. Much work has focussed on the mechanisms by which organic anions and organic cations are transported across the surface membranes of the proximal tubular cells, but little attention was paid to the routes by which these compounds cross the cell interior, the assumption being that simple diffusion across the cytoplasm was the only process necessary. We are using comparative renal models (proximal tubules from lower vertebrates and invertebrates and renal cells in culture) in combination with fluorescence microscopy (conventional and confocal), video imaging and intracellular microinjection to test that assumption. We have found that, after transport into renal cells, organic anions are distributed over two compartments: one that is diffuse and cytoplasmic, and a second that is punctate and vesicular. Sequestration in intracellular vesicles is not a result of endocytosis, but rather of uptake from the cytoplasm. Such uptake is concentrative, specific and energy- dependent. These findings indicate that the intracellular distribution of organic anions is not uniform and that, since a substantial fraction of cellular organic anions are sequestered, the average cellular concentrations measured in most experiments greatly overestimate cytoplasmic concentrations. Future studies will focus on: 1) characterizing the mechanism of vesicular organic anion sequestration in renal cells, 2) determining if organic cations are also sequestered and by what mechanism, 3) defining the role sequestration plays in overall renal xenobiotic secretion, and 4) searching for analogous intracellular secretion mechanisms in other specialized epithelia that accumulate and transport organic anions and cations, e.g., choroid plexus.

脊椎动物肾脏的一个重要功能是排泄 潜在的有毒化学品，如细胞新陈代谢的废物， 外源生物和外源代谢物。这主要发生在 近端小管，肾脏转运系统清除有机阴离子和 来自肾小管周围毛细血管的有机阳离子，并将它们输送到 肾小管上皮细胞进入管腔。很多工作都集中在 有机阴离子和有机阳离子的运输机制 穿过近端肾小管细胞的表面膜，但很少 人们注意到这些化合物通过细胞的途径 内部，假设是简单的跨细胞质扩散 是唯一需要的程序。我们正在使用比较的肾脏模型 (低等脊椎动物和无脊椎动物的近端小管和肾细胞 在培养中)结合荧光显微镜(常规和 共聚焦)、视频成像和细胞内微注射来测试 假设。我们发现，在转运到肾细胞后，有机的 阴离子分布在两个隔间中：一个是弥散的，另一个是 细胞质的，第二个是点状和泡状的。封存于 细胞内的小泡不是内吞作用的结果，而是摄取的结果 从细胞质中。这种吸收是集中的、具体的和能量的- 依附的。这些发现表明，细胞内分布的 有机阴离子并不均匀，因为很大一部分 细胞有机阴离子被隔离，平均细胞 大多数实验中测得的浓度大大高估了 细胞质浓度。未来的研究将集中在以下几个方面：1) 膜泡状有机阴离子吸附机理的研究 肾细胞，2)确定有机阳离子是否也被隔离，并通过 什么机制，3)确定隔离在整个肾脏中所起的作用 异种生物分泌物，以及4)寻找类似的细胞内分泌物 在其他特化上皮中积累和分泌的分泌机制 运输有机阴离子和阳离子，例如脉络丛。