ROLE OF ALTERED MEMBRANE FUNCTION IN XENOBIOTIC TOXICITY

我们已经研究了机制，能量学，和外源性敏感性， 肾有机阴离子（OA）转运，主要系统，其中管理 消除许多有毒的异生物质。 离体基底外侧膜（BLM） 囊泡的研究表明，BLM OA运输是一个复杂的，三级 活性过程，通过1）Na 泵，2）Na/α-酮戊二酸（α-KG）共转运和3）OA/α-KG 交易所 BLM囊泡还提供了一个模型的机制评估， 外源物质的膜效应。 例如，脱氢松香酸 （DHAA），纸浆厂废水的主要成分，被证明是一种有效的 OA转运的竞争性抑制剂。 然而，它也明显减少了 被动膜通透性因此，它减缓了施加离子的衰减， 梯度，其次是受激梯度驱动的Na/α-KG 共转运，增加Na/α-KG驱动力的作用 偶联OA转运和部分补偿其直接抑制 方面的影响. OA的腔出口主要通过载体发生 介导的、潜在驱动的途径。 管腔阴离子交换，例如，OH/OA， 在OA分泌中仅发挥有限的作用，相反， 在尿酸盐重吸收中起重要作用。 延伸隔离膜 研究中，OA转运的间接Na偶联在完整的 几个物种的上皮细胞。 此外，OK细胞，一种培养的细胞， 显示许多近端肾小管功能的线，也显示显示 Na/alpha-KG/OA转运，在细胞系中的首次此类证明。 因此，OK细胞提供了一种研究α-KG代谢控制的手段 水平和OA运输。 完整的肾上皮也显示离散 运输过程中OA在细胞内的囊泡积聚， 细胞内区室化可能在 跨上皮OA转运和/或保护细胞内 运输过程中的完整性。 最后，编码OA的肾mRNA 运输系统被分离，大小分级，并在非洲爪蟾中表达 卵母细胞，为制备所需的核苷酸探针奠定基础 用于该系统的生物化学表征及其 发展和监管。

We have examined the mechanism, energetics, and xenobiotic sensitivity of renal organic anion (OA) transport, the major system which governs the elimination of many toxic xenobiotics. Isolated basolateral membrane (BLM) vesicles studies demonstrated that BLM OA transport is a complex, tertiary active process, indirectly coupled to metabolic energy through 1) the Na pump, 2) Na/alpha-ketoglutarate (alpha-KG) cotransport and 3) OA/alpha-KG exchange. BLM vesicles also provided a model for mechanistic assessment of the membrane effects of xenobiotics. For example, dehydroabietic acid (DHAA), a major component of pulp mill effluent, was shown to be a potent competitive inhibitor of OA transport. However, it also markedly reduced passive membrane permeability. thus, it slowed decay of imposed ion gradients, and, secondarily, stimulated gradient driven Na/alpha-KG cotransport, effects which increased the driving force for Na/alpha-KG coupled OA transport and partially compensated for its direct inhibitory effects. Luminal exit of OA was shown to occur predominantly via a carrier mediated, potential driven pathway. Luminal anion exchange, e.g., OH/OA, was shown to play only a limited role in OA secretion, playing instead an important role in urate reabsorption. Extending the isolated membrane studies, indirect Na-coupling of OA transport was demonstrated in intact epithelia from several species. Furthermore, the OK cell, a cultured cell line displaying many proximal tubular functions, was also shown to display Na/alpha-KG/OA transport, the first such demonstration in a cell line. Thus, OK cells provide a means to study metabolic control of alpha-KG levels and OA transport. Intact renal epithelia also showed discrete vesicular accumulation of OA within the cells during transport, raising the possibility that intracellular compartmentalization may play a role in transepithelial OA transport and/or in protection of intracellular integrity during transport. Finally, renal mRNA coding for the OA transport system was isolated, size fractionated, and expressed in Xenopus oocytes, setting the stage for preparation of the nucleotide probes needed for biochemical characterization of this system and assessment of its development and regulation.