ELECTRICAL AND CONTRACTILE PROPERTIES OF MUSCLE

在脊椎动物的抽搐肌纤维中，收缩通常由 横向管状系统的膜的去极化。这 导致钙从肌浆网（SR）内部运动到 在肌浆中，它可以与肌钙蛋白上的Ca调节位点结合， 收缩可以发生。建议的研究的长远目标 本申请旨在了解（A）Ca如何从SR移动到 肌浆是由跨膜的电位差调节的， 横管系统和（B）钙发生了什么变化后，它是 释放到肌浆中实验将在青蛙切口上进行 双凡士林间隙室中安装的抽搐纤维。变化 肌浆Ca将在以下任一之后用Ca指示剂测量 动作电位刺激或电压钳去极化。电流从 膜内电荷运动，这被认为是发挥作用， 调节SR钙释放的管状膜，将测量与 电压钳方法。 具体目标是： 1.为了测量从切断的肌纤维的SR释放的Ca，其中游离的 [Ca]被大浓度的 高亲和力Ca指示剂。 2.为了测量SR释放后对Ca的再摄取， 肌纤维中游离[Ca]被缓冲到几乎恒定的水平， 高浓度的高亲和力Ca指示剂。 3.为了测量游离[Ca]被切断的肌纤维中的电荷运动， 缓冲到几乎恒定的水平，由高浓度的 亲和Ca指示剂或缓冲液。 4.同时测量和比较电荷运动，或某些成分 它的，和SR钙释放在切断肌纤维，其中游离[Ca]是 缓冲到几乎恒定的水平，由高浓度的 亲和力Ca指示剂。 5.同时测量和比较电荷运动，或某些成分 在更正常的情况下， 生理条件下，游离[Ca]不被 外源性Ca缓冲液。

In vertebrate twitch muscle fibers, contraction is normally activated by a depolarization of the membranes of the transverse tubular system. This leads to a movement of Ca from inside the sarcoplasmic reticulum (SR) into myoplasm where it can bind to the Ca-regulatory sites on troponin so that contraction can occur. The longterm objectives of the research proposed in this application are to understand (A) how Ca movement from the SR into myoplasm is regulated by the potential difference across the membranes of the transverse tubular system and (B) what happens to the Ca after it is released into the myoplasm. The experiments will be carried out on frog cut twitch fibers mounted in a double Vaseline-gap chamber. Changes in myoplasmic Ca will be measured with Ca indicators after either action-potential stimulation or voltage-clamp depolarization. Currents from intramembranous charge movement, which are thought to play a role in the regulation of SR Ca release by the tubular membranes, will be measured with the voltage-clamp method. The specific aims are: 1. To measure Ca release from the SR of cut muscle fibers in which free [Ca] is buffered to a nearly constant level by a large concentration of a high affinity Ca indicator. 2. To measure the reuptake of Ca by the SR, after its release, in cut muscle fibers in which free [Ca] is buffered to a nearly constant level by a large concentration of a high affinity Ca indicator. 3. To measure charge movement in cut muscle fibers in which free [Ca] is buffered to a nearly constant level by a large concentration of a high affinity Ca indicator or buffer. 4. To simultaneously measure and compare charge movement, or some component of it, and SR Ca release in cut muscle fibers in which free [Ca] is buffered to a nearly constant level by a large concentration of a high affinity Ca indicator. 5. To simultaneously measure and compare charge movement, or some component of it, and SR Ca release in cut muscle fibers under more normal physiological conditions in which free [Ca] is not heavily buffered by extrinsic Ca buffers.