METABOLICALLY COUPLED ION CHANNEL INTERACTIONS IN ISLETS

描述（改编自申请人摘要）：非胰岛素依赖型 糖尿病患者胰岛素分泌受损。 我们的假设是 异常胰岛电活动是一种内在损伤， 造成了这种损害。 胰岛是一个合胞体， 含有不同激素的电耦合细胞。 高架 葡萄糖、B细胞离子通道相互作用产生爆发和振荡 电活动模式，介导循环钙摄取， 对正常的胰岛素分泌很重要。 以前的研究试图 根据生物物理特性了解整个胰岛的破裂， 单个B细胞的离子通道 然而，目前尚不清楚是否 单个B细胞破裂或它们的不同离子通道如何相互作用来介导 细胞放电 我们知识上的这些重大差距使我们无法 了解异常离子通道机制是如何导致 糖尿病动物的爆裂和分泌。 为了解决这个问题，我们将 (1)将电压波形施加到单个电压钳位小鼠B细胞， 模拟膜电位和细胞内离子的变化 在爆发中遇到的（爆发波钳位），以确定B细胞离子如何 通道电流在猝发过程中发生变化;（2）测试注入电流 不同的人工电压和时间依赖性离子通道电流进入 电流箝位的B细胞影响细胞放电（动态箝位）。 初步 数据表明单个B细胞具有不均匀的电活动， 包括突发，并且可以分为三个子类。 建模与 用动态钳对独立细胞进行人工电偶联， 确定耦合如何影响B细胞放电。 一种新的胰岛破裂模型 将通过将观察到的具有非均匀点火的细胞 实验性的 同时膜片钳和电流分析法将确定 爆发与尖峰是否优先增加胰岛素分泌。 这些目标的实现将确定B细胞通道， 在正常和糖尿病胰岛的电活动的基础，并可能导致 糖尿病的新疗法基于对这些通道的操纵。

DESCRIPTION (Adapted from applicant's abstract): Non-insulin-dependent diabetics have impaired insulin secretion. Our general hypothesis is that abnormal pancreatic islet electrical activity is an intrinsic lesion that contributes to this impairment. Islets are a syncytium of electrically-coupled cells containing different hormones. In elevated glucose, B-cell ion channels interact to produce bursting, and oscillatory electrical activity pattern which mediates cyclic Ca uptake and which is important for normal insulin secretion. Previous studies have attempted to understand bursting of whole islets based on the biophysical properties of the ion channels of single B-cells. However, it has not been clear whether single B-cells burst or how their different ion channels interact to mediate cell firing. These significant gaps in our knowledge prevent us from understanding how abnormal ion channel mechanisms underlie the abnormal bursting and secretion of diabetic animals. To address this issue, we will (1) apply voltage wave forms to single voltage-clamped mouse B-cells that simulate the changes in membrane potential and intracellular ions encountered in bursting (burstwave clamping) to determine how B-cell ion channel currents change during bursting; and (2) test how injecting different artificial voltage- and time-dependent ion channel currents into current-clamped B-cells affects cell firing (dynamic clamping). Preliminary data suggest that single B-cells have heterogeneous electrical activity, including bursting, and can be grouped into three subclasses. Modeling and artificial electrical coupling of independent cells with dynamic clamp will determine how coupling affects B-cell firing. A new model of islet bursting will be made by coupling cells having the heterogenous firing observed experimentally. Simultaneous patch clamping and amperometry will determine whether bursting vs. spiking preferentially augments insulin secretion. Accomplishment of these aims will identify the B-cell channels which underlie electrical activity in normal and diabetic islets and may lead to new therapies for diabetes based on manipulating these channels.