Single Ion Channels from Teleost Intestinal Epithelium

脊椎动物的肠道上皮起着重要的屏障作用，控制离子、营养物质和水进入动物体内。该项目的主要目标是确定肠道上皮中特定的离子通道对跨上皮化学和电势分布的贡献机制，而跨上皮化学和电势分布是吸收离子和营养物质的驱动力。这些位于顶端(腔)和基侧(血液侧)细胞膜上的离子通道，与离子转运体和肠上皮细胞间细胞旁通路的阻力特性一起，是跨上皮电位谱的基础。激素和药物可以通过直接或间接作用于膜通道和载体来改变转运过程。利用细胞内微电极、膜片钳和重组膜泡技术，我们将研究硬骨、虾虎鱼、肠道中这些特定离子通道的电压依赖性和化学依赖性。这些生物物理和生理学研究将增加对肠道在液体和电解质平衡中的作用的了解。脊椎动物的肠道不仅能吸收食物中的营养，还能调节盐分和水分的平衡。这一点在适应海水的鱼类中尤其明显，因为在这些鱼类中，体内的水有丢失的趋势，而盐分则从含盐的环境中获得。虎鱼是一种小型鱼类，具有适应环境中广泛盐分浓度的生理能力，因此是一种非常有用的生物，可以用来研究盐分和水平衡调节的离子传输机制。关于盐分在这种有趣的鱼的整个肠道中的运输，人们已经了解了很多，但离子通过这种组织膜的详细途径和调节机制还没有弄清楚。这项研究将应用最新的膜片钳电记录方法，结合生化分析激素对参与盐运输的离子通道的细胞内影响。这项研究的结果将对我们理解肠道细胞的生理功能具有重要意义。

The intestinal epithelium of vertebrates serves an important barrier function controlling the movement of ions, nutrients, and water into the animal. The major objective of the proposed project is to determine the mechanisms by which specific ion channels in the intestinal epithelium contribute to the transepithelial chemical and electrical potential profiles which serve as the driving forces for absorption of ions and nutrients. These specific ion channels located in the apical (luminal) and basolateral (blood side) cell membranes, together with ion transporters and the resistance properties of the paracellular pathway between intestinal epithelial cells are the bases of the transepithelial potential profiles. Hormonal and pharmacological agents can alter transport processes through effects directly or indirectly on membrane channels and carriers. Using intracellular microelectrode, patch clamp and reconstituted membrane vesicle techniques, we will examine the voltage- and chemical-dependence of these specific ion channels in the teleost, goby, intestine. These biophysical and physiological investigations will increase understanding of the role of the intestine in fluid and electrolyte balance. The intestine of vertebrate animals serves not only to absorb nutrients from food, but also to regulate salt and water balance. This is particularly clear in seawater-adapted fishes in which there is a tendency for body water to be lost and salts gained from the salty environment. The goby is a small fish that has the physiological ability to adapt to a wide range of salt concentrations in its environment, and therefore is a very useful organism in which to study the ion transport mechanisms underlying the regulation of salt and water balance. Much has been learned about the transport of salts across the whole intestine of this interesting fish, but the detailed pathways and mechanisms of regulation of passage of ions across the membranes of this tissue have not yet been worked out. This study will apply the latest methods of patch clamp electrical recording in combination with biochemical analysis of the intracellular effects of hormones that affect ion channels involved in salt transport. The results of this research will contribute significantly to our understanding of the physiological function of intestinal cells.