PROXIMAL COLON--A DISTINCT TRANSPORT EPITHELIUM

钠（Na）吸收在重要生物功能中的调节。 肠道钠吸收紊乱导致腹泻病， 是全球发病率和死亡率较高的原因。肠道 在其机制中表现出显著的节段异质性， 钠吸收。盲肠的产电钠率很高 吸收，既不耦合到阴离子或营养素，也不阻止 阿米洛利一些证据表明，盲肠钠吸收可能 发生通过钠通道显着修改从转运 在远端结肠和其他紧密上皮中发现，包括1）抑制 阿米洛利类似物非那敏的电流和钠吸收， ii）心尖Na电导的电生理学证明。通过 各种技术（Ussing室，微电极，膜片钳），我们 将描述盲肠钠的宏观和微观特征， 吸收，占其独特的传输特性。近侧 结肠通过Na-H交换以电中性吸收Na。几个监管机构 近端结肠中的Na吸收已被确定，包括降低 钠在洗澡媒体，去除碳酸氢盐，糖皮质激素和 短链脂肪酸，其对Na转运具有特异性影响， 近端结肠我们将研究细胞内的适应 通过使用与跨上皮转运变化相关的 电生理技术（微电极）、pH统计和荧光 染料。结肠中主要的管腔阴离子是短链脂肪酸阴离子， 酸（SCFA）。它们在离体离子转运中的作用尚不清楚 定义;然而，它们与Na运输的关系和作为一种 热量重要来源（“结肠补救”）是 近端结肠和盲肠的功能。我们将研究SCFA运输， 体外确定吸收是否主要是跨细胞的， 细胞旁的，在酸或离子化的形式和关系，钠 运输盲肠和近端肠段的输运能量模型 冒号提供了将这些特定适应 肠道转运蛋白的生物学功能，并将其与 其他表现出产电或电中性Na+的上皮细胞 吸收通过描述盲肠的特定运输过程， 和近端结肠，我们将更好地了解 肠道的节段异质性，并深入了解结肠的 液体和电解质的处理， 腹泻和结肠作为营养器官的作用。

Regulation of sodium (Na) absorption in a vital biological function. Derangements of intestinal Na absorption lead to diarrheal diseases, a cause of significant worldwide morbidity and mortality. The gut demonstrates a significant segmental heterogeneity in its mechanisms of Na absorption. The cecum exhibits a high rate of electrogenic Na absorption, neither coupled to anions or nutrients, nor blocked by amiloride. Several lines of evidence suggest that cecal Na absorption may occur through a Na channel significantly modified from the transporter found in distal colon and other tight epithelia, including 1) inhibition of both current and Na absorption by the amiloride analogue phenamil and ii) electrophysiologic demonstration of an apical Na conductance. Through a variety of techniques (Ussing chamber, microelectrodes, patch clamp) we will characterize the macroscopic and microscopic features of cecal Na absorption that account for its distinct transport properties. Proximal colon absorbs Na electroneutrally by Na-H exchange. Several regulators of Na absorption in proximal colon have been identified, including lowered Na in the bathing media, removal of bicarbonate, glucocorticoids and short-chain fatty acids, which have effects on Na transport specific to the proximal colon. We will investigate the intracellular adaptions associated with changes in transepithelial transport by using electrophysiologic techniques (microelectrodes), pH stat and fluorescent dyes. The predominant luminal anions in the colon are short-chain fatty acids (SCFA). Their role in ion transport in vitro has yet to be clearly defined; however, their relation to Na transport and potential role as a significant source for calories ("colonic salvage") are major factors in the function of proximal colon and cecum. We will study SCFA transport in vitro to determine whether absorption is principally transcellular or paracellular, in the acid or ionized form and the relationship to Na transport. The energing models for transport in the cecum and proximal colon provide the opportunity to relate the specific adaptions of these intestinal transporters to their biological function and compare these to other epithelia that exhibit electrogenic or eletro-neutral Na absorption. By characterizing the specific transport processes of cecum and proximal colon, we will achieve a better understanding of the segmental heterogeneity of the gut and gain insight into the colon's handling of fluid and electrolytes, the regional pathophysiology of diarrhea and the role of the colon as a nutritive organ.