ROLE OF ALTERED MEMBRANE FUNCTION IN XENOBIOTIC TOXICITY

有机阴阳离子(OC)的肾脏分泌系统起支配作用 消除大多数较小的(&lt；500mol.wt.)外国化学品。我们有 以前的研究表明，骨质疏松症的转运与代谢是间接耦合的 通过Na/α-酮戊二酸(α-KG)共运输的能量和 OA/AlphaKG交换。我们目前正在检查a)质膜和 与分泌运输相关的细胞内事件(在 与D.S.Miller的合作)，b)这些系统的分子生物学， C)肾外OA和OC转运的能量学和机制，以及d) OA和OC在肾脏和肾外部位的毒理学研究脉络膜 神经丛调节潜在毒性的骨性关节炎和骨质疏松症的运输。 血-脑脊液屏障进入血液，随后被肾脏或 肝脏。我们开发了一种单层培养的神经丛制剂 在体外主动转运骨钙素和骨钙素。除了助熔剂研究 它们已经表征了这个的基本传输属性 上皮细胞，我们已经显示了对这两类异源物质的介导性摄取 变成细胞内的小泡。显示含有囊泡的OC可以移动 到细胞的基底外侧(血液侧)，并释放它们的 内容物，表明囊泡运动直接参与了 跨上皮通量--分泌物中的第一个这样的证明 上皮组织。细胞基底外侧面上OC的囊泡释放 被微管的去极化可逆地破坏了 诺可达唑。我们还证明了这种速度和效率 测定了完整肾小管上皮细胞对油酸的分泌转运 根据细胞内α-KG的浓度和梯度 基底侧膜。反过来，细胞质αKG浓度是 由其细胞内的隔间作用决定(主要是 线粒体)和代谢。最后，表达克隆和聚合酶链式反应探针 已用于筛选从大鼠肾脏中制备的cDNA文库 MRNA.这些研究为鉴定和克隆该基因奠定了基础 编码这两个重要排泄物运输系统的基因。

Renal secretory systems for organic anions (OA) and cations (OC) govern the elimination of most small (<500mol.wt.) foreign chemicals. We have previously shown that OA transport is indirectly coupled to metabolic energy through Na/alpha-ketoglutarate (alphaKG) co-transport and OA/alphaKG exchange. We are currently examining a) plasma membrane and intracellular events associated with secretory transport (in collaboration with D.S. Miller), b) molecular biology of these systems, c) energetics and mechanisms of extrarenal OA and OC transport, and d) toxicology of OA and OC in kidney and extrarenal sites. The choroid plexus mediates transport of potentially toxic OA and OC across the blood-CSF barrier into the blood for subsequent elimination by kidney or liver. We have developed a monolayer cultured plexus preparation which actively transports OA and OC in vitro. In addition to flux studies which have characterized the basic transport properties of this epithelium, we have shown mediated uptake of both classes of xenobiotics into intracellular vesicles. OC containing vesicles were shown to move to the basolateral side of the cell (blood side) and release their contents, indicating direct participation of vesicular movement in transepithelial flux - the first such demonstration in a secretory epithelium. Vesicular release of OC at the basolateral face of the cell was reversibly disrupted by depolimerization of microtubules with nocodazole. We have also demonstrated that the rate and effectiveness of secretory transport of OA by intact renal tubular cells was determined by the intracellular concentration and gradient of alphaKG across the basolateral membrane. In turn the cytoplasmic alphaKG concentration was determined by its intracellular compartmentation (primarily into mitochondria) and metabolsim. Finally, expression cloning and PCR probes have been utilized to screen a cDNA library prepared from rat kidney mRNA. These studies are preliminary to identification and cloning of the genes coding for these two important excretory transport systems.