PROXIMAL COLON--A DISTINCT TRANSPORT EPITHELIUM

钠(Na)吸收的调节具有重要的生物功能。 肠道钠吸收紊乱导致腹泻病 造成世界范围内重大发病率和死亡率的原因。胆量 在其机制中显示出显著的节段性异质性 钠吸收。盲肠表现出很高的生电性钠 吸收的，既不与阴离子或营养物质结合，也不被 阿米洛利。一些证据表明盲肠对钠的吸收可能 通过从转运体显著修改的钠通道发生 见于远端结肠和其他致密上皮，包括1)抑制 阿米洛利类似物非那米和钠对电流和钠吸收的影响 Ii)心尖部钠电导的电生理学证明。穿过 各种技术(使用小室、微电极、膜片钳) 将表征盲肠钠的宏观和微观特征 吸收，这说明了它独特的传输特性。近端 结肠通过Na-H交换以电子中性方式吸收Na。几个监管机构 近端结肠的NA吸收已被发现，包括降低 沐浴介质中的钠，去除小苏打，糖皮质激素和 短链脂肪酸，它对钠的转运有特殊的影响 近端结肠。我们将研究细胞内的适应 与跨上皮运输的变化相关，通过使用 电生理技术(微电极)、pH调节器和荧光 染料。结肠中主要的腔内阴离子是短链脂肪。 酸(SCFA)。它们在体外离子转运中的作用尚不清楚。 然而，它们与钠转运的关系以及作为一种潜在的 卡路里的重要来源(“结肠保留物”)是 近端结肠和盲肠的功能。我们将研究SCFA的运输。 以确定吸收是否主要是跨细胞的或 以酸性或电离形式存在的细胞旁及其与钠的关系 运输。盲肠和近端转运的能量模型 冒号提供了一个机会来描述这些特定的改编 肠道转运体的生物学功能，并与 其他显示生电或中性钠的上皮细胞 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 肠道的节段性异质性和对结肠的洞察 液体和电解质的处理，局部病理生理学 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.