ION ACTIVITIES AND MEMBRANE POTENTIAL IN HEART

拟议的研究将检查膜电位(Em)的基础。 兔心房室结(AVN)。AVN中的Em低于AvN中的 心房、心室或浦肯野纤维，对心脏功能的改变相对不敏感 胞外钾活性。 这些发现的解释是假设细胞内的氯化物 在Em处的被动分布和PCL/PK的活性大于所需的， 氯离子渗透率与钾渗透率之比相对较小。 很高。然而，细胞内氯的活性和PCL/PK都不是已知的。 或者，就像我在这里假设的那样，细胞内的钾活动 可能低于其他心脏组织，并且可能强烈依赖于 胞外钾活性。 提出的实验将对这两个假设进行批判性的检验。钾 离子选择微电极和氯离子选择微电极将 用于直接测定细胞内钾和氯化物的活性。 将计算PCL/PK。Em与细胞外的关系 将测定钾和氯化物的活度。对…的控制 细胞内钾的活性将通过改变其胞外活性来研究。 活动。细胞内氯活性的控制将通过以下方式进行研究 改变钾和氯化物的胞外活性。 这些实验将有助于理解动静脉络膜的基础和 将提供必要的基准数据，以了解更复杂的电气、 药理和病理事件。

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.