ION ACTIVITIES AND MEMBRANE POTENTIAL IN HEART

拟议的研究将检查膜电位（Em）的基础， 房室结（AVN）。 AVN的Em低于 心房、心室或浦肯野纤维的变化相对不敏感， 细胞外钾活性 这些发现可以通过假设细胞内氯离子 活性大于在Em处被动分布所需的活性，并且PCl/PK， 氯离子渗透率与钾离子渗透率之比相对 高 然而，细胞内氯化物活性和PCl/PK均未知。 或者，正如我在这里所假设的，细胞内钾活性 可能低于其他心脏组织，并且可能强烈依赖于 细胞外钾活性 所提出的实验将严格检验这两个假设。 钾 离子选择性微电极和氯离子选择性微电极将 用于直接测定细胞内钾离子和氯离子的活性。 将计算PCl/PK。 Em与细胞外 将测定钾和氯的活性。 的控制 细胞内钾活性将通过改变其细胞外 活动 细胞内氯离子活性的控制将通过以下方法进行研究： 改变钾和氯的细胞外活性。 这些实验将导致对AVN中Em的基础的理解， 将提供必要的基线数据，以了解更复杂的电气， 药理学和病理学事件。

The proposed research will examine the basis for membrane potential (Em) in the atrio-ventricular node (AVN) of rabbit heart. Em in the AVN is lower than in atrium, ventricle or Purkinje fiber and is relatively insensitive to changes in extracellular potassium activity. These findings have been explained by postulating that intracellular chloride activity is greater than required by passive distribution at Em and that PCl/PK, the ratio of chloride permeability to potassium permeability, is relatively high. However, neither intracellular chloride activity nor PCl/PK are known. Alternatively, as I have postulated here, the intracellular potassium activity may be lower than in other cardiac tissues, and it may be strongly dependent on extracellular potassium activity. The experiments proposed will critically test these two hypotheses. Potassium ion-selective microelectrodes and chloride ion-selective microelectrodes will be used to measure the intracellular activities of potassium and chloride directly. PCl/PK will be calculated. The relationships between Em and both extracellular potassium and chloride activities will be determined. The control of intracellular potassium activity will be studied by varying its extracellular activity. The control of intracellular chloride activity will be studied by varying the extracellular activities of potassium and chloride. These experiments will lead to an understanding of the basis of Em in AVN and will provide the baseline data necessary to understand more complex electrical, pharmacological, and pathological events.