SODIUM CHANNELS IN COLONIC EPITHELIAL CELLS

上皮钠通道调节上皮细胞重吸收钠的速率 如肾脏集合管和远端结肠，因此 维持盐分和液体的动态平衡。这些频道有 在肾小管和培养的单通道水平上进行了研究 肾细胞，但不在结肠里。这一空白将由以下人员填补 分离大鼠宏观电流和单通道电流的研究 使用膜片钳技术的结肠癌细胞。一、实施的条件和方法 用于研究这些电流的细胞分离将得到优化。 将寻求既保持形态极性又保持形态极性的条件 以及用阿米洛利评估的钠通道的功能- 灵敏的全细胞电流。然后，在这些元素中的相似程度 结肠经络的功能特性与肾脏功能特性的比较 将会被检查。关于跨上皮运输的变化我们知道得很多。 动物发育过程中结肠率的变化 盐皮质激素状态。结肠中钠通道的行为将是 在这些条件下研究，看看这些变化在多大程度上反映了 渠道活动的变化，以及如何在 在这种情况下。将监控这些通道的特性 在产后发育的三个不同阶段：哺乳(10天 老年)、断奶(25日龄)和成年。选择性、电流-电压 单通道电导与开通动力学的关系 将评估Na通道的关闭情况。这些研究将集中在 所观察到的运输变化是否反映了质的问题 通道差异(电导、选择性、开放概率)或 频道数量的差异。最后，渠道的整治 通过肾上腺皮质类固醇激素的研究。这些 调查将区分定性或定量 基础状态和刺激状态下通道的差异 含盐皮质激素和糖皮质激素。这些研究将给出 结肠离子转运的基本机制及其研究进展 调节，并将有助于了解在哪些疾病上皮 运输是错乱的，比如腹泻和囊性纤维化。

Epithelial Na channels regulate the rate of Na reabsorption by epithelia such as the renal collecting tubule and the distal colon, and therefore serve to maintain salt and fluid volume homeostasis. These channels have been studied at the single-channel level in renal tubules and in cultured kidney cells, but not in the colon. This gap will be filled by investigating both macroscopic and single-channel currents in isolated rat colonocytes using patch-clamp techniques. First, conditions and methods of cell isolation for the study of these currents will be optimized. Conditions will be sought which preserve both the morphological polarity of the cells and the function of the Na channels as assessed by amiloride- sensitive whole-cell currents. Then the degree of similarity in the functional properties of colonic channels compared to those of the kidney will be examined. Much is known about changes of transepithelial transport rates in the colon with development of the animal and with mineralocorticoid status. The behavior of Na channels in the colon will be studied under these conditions to see to what extent these changes reflect changes in channel activity, and how channel activity is modulated under these circumstances. The characteristics of the channels will be monitored at three different stages of post-natal development: suckling (10 days old), weanling (25 days old) and adult. The selectivity, current-voltage relationship, single-channel conductance and kinetics of opening and closing of Na channels will be assessed. These studies will focus on the question of whether the observed changes in transport reflect qualitative differences in channels (conductance, selectivity, open probability) or differences in the number of channels. Finally, the regulation of channels by adrenal corticosteroid hormones will be investigated. These investigations will distinguish between qualitative or quantitative differences in the channels under basal conditions and during stimulation with mineralocorticoids and glucocorticoids. These studies will give insights into the basic mechanisms of colonic ion transport and its regulation, and will help in understanding diseases in which epithelial transport is deranged such as diarrhea and cystic fibrosis.