CELLULAR MECHANISMS OF XENOBIOTIC TRANSPORT

异生物运输的细胞机制

• 批准号: 3855986
• 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/3855986
• 关键词: anions; bioenergetics; cations; choroid plexus; cytoplasm; endocytosis; environmental toxicology; fluorescence microscopy; ion transport; organic chemicals; renal toxin; renal tubule; vesicle /vacuole; video recording system

The vertebrate renal proximal tubule mediates excretion of potentially toxic, charged organic compounds, e.g., metabolic wastes, environmental pollutants, drugs and their polar metabolites. Previous work which focussed on the separate mechanisms by which organic anions and cations cross the surface membranes of the renal tubular cells paid little attention to the routes by which these compounds traverse the cell interior, the assumption being that diffusion through the cytoplasm is the only process necessary. We are using comparative renal models (proximal tubules from lower vertebrates and invertebrates and mammalian cells in culture) combined with video imaging, fluorescence microscopy and intracellular microinjection to test that assumption. Our studies show that after organic anions enter renal cells they both diffuse through the cytoplasm and are taken u by vesicles. Sequestration in vesicles involves concentrative and specific uptake from the cytoplasm rather than endocytosis from the medium. These findings indicate that the intracellular distribution of organic anions is not uniform an that the cellular concentration measured in tracer uptake studies may overestimated cytoplasmic activity. In addition, they suggest that renal cells could use intracellular compartmentation to reduce levels of potentially toxic chemicals in the cytoplasm. Future studies will focus on: 1) defining the mechanisms and energetics of vesicular accumulation in renal cells, 2) determining the role of sequestration in overall organic anion secretion, 3) evaluating the possibility that sequestration underlies the extremely high levels of organic cations found proximal tubule cells, and 4) searching for intracellular sequestration mechanisms in other epithelia which accumulate and transport organic anions and cations, e.g., choroid plexus.

脊椎动物肾近曲小管介导潜在的排泄 有毒、带电有机化合物，例如代谢废物、环境废物 污染物、药物及其极性代谢物。 之前的作品有哪些 专注于有机阴离子和阳离子的不同机制 穿过肾小管细胞表面膜的费用很少 注意这些化合物穿过细胞的途径 内部，假设通过细胞质的扩散是 只有必要的过程。 我们正在使用比较肾脏模型（近端 来自低等脊椎动物和无脊椎动物以及哺乳动物细胞的小管 培养）结合视频成像、荧光显微镜和 细胞内显微注射来检验这一假设。 我们的研究表明 有机阴离子进入肾细胞后，它们都通过肾细胞扩散 细胞质并被囊泡摄取。 囊泡中的隔离涉及 从细胞质集中和特异性摄取，而不是 来自培养基的内吞作用。 这些发现表明 有机阴离子在细胞内分布不均匀 示踪剂摄取研究中测量的细胞浓度可能被高估 细胞质活性。 此外，他们认为肾细胞可以利用 细胞内分隔以降低潜在毒性水平 细胞质中的化学物质。 未来的研究将集中于：1）定义 肾细胞中囊泡积累的机制和能量学，2) 确定封存在总体有机阴离子分泌中的作用， 3）评估封存是极端情况的可能性 近端小管细胞中发现高水平的有机阳离子，4) 寻找其他上皮细胞的细胞内隔离机制 积累和运输有机阴离子和阳离子，例如脉络膜 神经丛。