CELLULAR MECHANISMS OF XENOBIOTIC TRANSPORT

异生物运输的细胞机制

• 批准号: 3777571
• 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/3777571
• 关键词: active transport; animal tissue; biological models; fluorescence microscopy; intracellular transport; ion transport; kidney cell; membrane permeability; microinjections; microtubules; renal tubular transport; 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 mammalian renal cells in culture) in combination with fluorescence microscopy (conventional and confocal), video imaging, intracellular microinjection and isolated membrane vesicle techniques to test that assumption. We have found that, after transport into renal cells, organic anions and cations are distributed over two compartments: one is diffuse and cytoplasmic, and the second punctate and vesicular. Sequestration in intracellular vesicles is not a result of endocytosis, but rather of active uptake from the cytoplasm. Such uptake is concentrative, specific and energy-dependent. Thus, organic anions and cations are not uniformly distributed within cells, rather, for each, a substantial fraction is sequestered in vesicles. For organic anions, initial results indicate that these vesicles move through the cytoplasm in the secretory direction on microtubules and that this movement contributes substantially to the rate of net secretion. Future studies will focus on: 1) further characterizing the vesicular transport processes involved, 2) defining the role that vesicular transport plays in overall renal xenobiotic secretion, and 3) searching for analogous mechanisms in other specialized epithelia that accumulate and transport organic anions and cations, e.g., liver and choroid plexus.

脊椎动物肾脏的一个重要功能是排泄 潜在的有毒化学物质，如细胞的废物， 代谢、异生物质和异生物质代谢物。 发生这种情况 主要是在近端小管中，在那里肾脏转运系统将 来自管周毛细血管的有机阴离子和有机阳离子， 运输它们穿过肾小管上皮进入管腔。 许多工作 一直专注于有机阴离子和有机 阳离子通过近端细胞的表面膜传输， 肾小管细胞，但很少注意到的路线， 这些化合物穿过细胞内部，假设 穿过细胞质的简单扩散是唯一必需的过程。 我们使用比较肾脏模型（近端小管从下 脊椎动物和无脊椎动物以及培养的哺乳动物肾细胞）中， 与荧光显微术（常规和共焦）结合， 视频成像、细胞内显微注射和离体膜 囊泡技术来验证这一假设。 我们发现， 运输到肾细胞，有机阴离子和阳离子分布 在两个区室：一个是弥漫性和细胞质，第二个是 点状和囊状。 在胞内囊泡中的隔离不是 这是内吞作用的结果，而是从细胞质主动摄取的结果。 这种吸收是集中的、特异的和依赖能量的。 因此，在本发明中， 有机阴离子和阳离子在细胞内不是均匀分布的， 相反，对于每一种，相当大的一部分被隔离在囊泡中。 对于有机阴离子，初步结果表明，这些囊泡移动 通过细胞质沿微管分泌方向， 这一运动对净增长率的贡献很大， 分泌物 未来的研究将集中在：1）进一步表征 涉及的囊泡运输过程，2）定义的作用， 囊泡转运在整个肾脏异生物质分泌中起作用，以及3） 在其他特化上皮细胞中寻找类似的机制， 积累和运输有机阴离子和阳离子，例如，肝脏和 脉络丛