Regulation of Intestinal Na Absorption

性状（由申请方提供）：在哺乳动物小肠中，Na主要通过偶联NaCl吸收和绒毛细胞刷状缘膜上的Na-葡萄糖共转运（SGLT-1）吸收。耦合的NaCl吸收通过Na：H（特别是NHE 3）和Cl：HCO 3交换的双重操作发生。一氧化氮（NO）是最具生物活性的分子之一，对正常肠道中NHE 3和SGLT-1的调节尚不清楚。我们证明，无论是在体内在兔和/或在体外抑制在大鼠肠上皮细胞，抑制NO抑制绒毛细胞BBM SGLT-1和刺激NHE 3。SGLT-1的抑制机制是通过改变蛋白质的糖基化来特异性降低其对葡萄糖的亲和力。与此相反，NHE3的刺激继发于BBM转运体数量的增加，通过增加BBM NHE3的转录和合成。已经表明，抑制NO调节NHE3和SGLT-1，下一个合乎逻辑的问题是在NO的生理增加过程中发生了什么。事实上，迄今为止的结果表明，BBM NHE3和SGLT-1可能是由NO补偿调节，以维持细胞Na稳态。这些观察结果让我们提出了一个最新颖的问题--这两种BBM转运蛋白能否直接相互调节？这是一种在肠道运输生理学中没有描述过的现象。鉴于这一背景，这一建议的总体假设是，在肠细胞BBM的两个主要的钠吸收途径通过NO和/或直接相互调节，以维持细胞的钠稳态。因此，本提案的总体目的是确定NO和/或直接调节肠上皮细胞BBM NHE 3和SGLT-1的补偿性相互机制。特别是使用体内和体外模型的组合，采用互补的生理和分子技术与适当的药理学试剂和特定的分子试剂，我们将：1。阐明增强的NO介导的BBM NHE3和SGLT-1和2的调节机制。确定BBM NHE3和SGLT-1相互直接调节的机制。这项研究将提供新的见解，是否两个主要的钠吸收途径在BBM的肠上皮细胞可以直接调节彼此的功能，以及如何NO介导的NHE3和SGLT-1的代偿性相互调节。钠同化对维持健康至关重要，对腹泻和高血压等多种常见疾病至关重要。同样，葡萄糖吸收不仅是必不可少的，因为碳水化合物代表了饮食中的主要营养素，而且还因为它在从糖尿病到肥胖症的各种常见疾病中很重要。总之，本提案中假设的两种主要钠吸收途径的独特和直接调节可以形成制定策略的基础，以促进电解质和营养素吸收不足，并在疾病状态下抑制电解质和营养素吸收。公共卫生相关性：肠道中的钠和葡萄糖同化对保持身体健康至关重要。它们的吸收在许多常见疾病中甚至更重要，包括腹泻、糖尿病、肥胖和高血压。一氧化氮是最具生物活性的分子之一，可介导钠和葡萄糖吸收的调节。事实上，我们的研究表明，主要负责钠和葡萄糖吸收的转运蛋白（SLGT-1和NHE 3）可能直接相互调节。更好地理解这两个主要的钠吸收途径的独特和直接的调节，在这个建议中假设可以形成的基础上，制定战略，以促进电解质和营养吸收不足，并抑制同样的疾病状态，这将是有利的。

DESCRIPTION (provided by applicant): In the mammalian small intestine Na is primarily absorbed by coupled NaCl absorption and Na-glucose co-transport (SGLT-1) on the brush border membrane of villus cells. Coupled NaCl absorption occurs via the dual operation of Na:H (specifically NHE3) and Cl:HCO3 exchange. The regulation of NHE3 and SGLT-1 in the normal intestine by nitric oxide (NO), one of the most biologically active molecules, was unclear. We demonstrated that whether in vivo in rabbits and/or in vitro inhibition in rat intestinal epithelial cells, inhibition of NO inhibited villus cell BBM SGLT-1 and stimulated NHE3. The mechanism of inhibition of SGLT-1 was by reducing its affinity for glucose specifically by altering the glycosylation of the protein. In contrast, NHE3 was stimulated secondary to an increase in BBM transporter numbers by an increase in the transcription and synthesis of BBM NHE3. Having shown that inhibition of NO regulates NHE3 and SGLT-1, the next logical question is what happens during physiological increases in NO. In fact, results to date indicate that BBM NHE3 and SGLT-1 may be compensatorily regulated by NO to maintain cellular Na homeostasis. These observations led us to ask a most novel question -- can these two BBM transport proteins directly regulate one another? A phenomenon here to fore not described in intestinal transport physiology. Given this background, the overall hypothesis of this proposal is that the two primary Na absorptive pathways in the enterocyte BBM regulate one another via NO and/or directly to maintain cellular Na homeostasis. Thus, the overall aim of this proposal is to determine the compensatory reciprocal mechanism of regulation of intestinal epithelial cell BBM NHE3 and SGLT-1 by NO and/or directly. Specifically using a combination of in vivo and in vitro models, employing complementary physiological and molecular techniques with appropriate pharmacological agents and specific molecular reagents we will: 1. Elucidate the enhanced NO mediated mechanism of regulation of BBM NHE3 and SGLT-1 and 2. Determine the mechanism of direct regulation of BBM NHE3 and SGLT-1 by each other. This study will provide novel insight into whether the two primary Na absorptive pathways in the BBM of intestinal epithelial cells can directly regulate the functioning of each other and how NO mediates the compensatory reciprocal regulation of NHE3 and SGLT-1. Na assimilation is essential to maintain health and it is critical for a wide range of common diseases such as diarrhea and hypertension. Similarly, glucose absorption is not only essential because carbohydrates represent the predominant nutrient in the diet, but also because it is important in a variety of common diseases from diabetes to obesity. In conclusion, the unique and direct regulation of the two primary Na absorptive pathways as hypothesized in this proposal could form the basis for developing strategies to promote electrolyte and nutrient absorption where deficient and inhibit the same in disease states where it would be advantageous. PUBLIC HEALTH RELEVANCE: Sodium and glucose assimilation in the intestine is essential to maintain good health. Their absorption is even more critical in numerous common diseases including diarrhea, diabetes, obesity and hypertension. Nitric oxide, one of the most biologically active molecules, may mediate the regulation of the absorption of sodium and glucose. In fact, our studies show that transporters primarily responsible for sodium and glucose absorption (SLGT-1 and NHE3) may directly regulate one another. Better understanding of the unique and direct regulation of these two primary Na absorptive pathways as hypothesized in this proposal could form the basis for developing strategies to promote electrolyte and nutrient absorption where deficient and inhibit the same in disease states where it would be advantageous.