The efflux of radioactive K and Cl ions was measured in cow Purkinje fibres and ventricular preparations of cow, cat and frog. The effect of K and Cl was studied by changing the extracellular K concentration between zero and 54 mM, and by substituting Cl ions by acetylglycinate, isethionate, benzenesulphonate, propionate and nitrate. 2. In the absence of Cl the rate coefficient for 42K efflux showed a pronounced fall, which was more pronounced the higher the K concentration. This effect was not related to the change in membrane potential. The rate coefficient for 42K efflux increased in the presence of higher extracellular K concentrations. 3. 36Cl efflux increased in the presence of reduced as well as increased extracellular K concentrations. 4. The calculated permeability coefficient for K (PK) was maximal at 5-4 mM-K, decreased slightly at higher K concentrations, but fell markedly in K-free solutions, (to about 1/5 of the value in 5-4 mM-K). In Cl-free medium PK reduced to 0-67 of the value in the Cl medium, irrespective of the K concentration. 5. The calculated PCl was greater in K-free and 16-2 mM-K than in 5-4 mM-K. 6. The ratio PK/PCl showed important changes as a function of extracellular K concentration: the value was 5 in 5-4 mM-K and fell to 2 and 0-5 respectively in 16-2 and K-free solutions. 7. The results suggest that part of the changes in membrane resistance measured by electrical methods in Cl-free media is due to a simultaneous decrease in K conductance.
摘要
对奶牛浦肯野纤维以及奶牛、猫和青蛙的心室标本中放射性钾离子和氯离子的外流进行了测量。通过将细胞外钾浓度在0至54 mM之间变化，以及用乙酰甘氨酸、羟乙基磺酸、苯磺酸盐、丙酸盐和硝酸盐替代氯离子，研究了钾离子和氯离子的作用。2. 在无氯离子的情况下，42K外流的速率系数显著下降，钾浓度越高，这种下降越明显。这种效应与膜电位的变化无关。在较高的细胞外钾浓度存在时，42K外流的速率系数增加。3. 在细胞外钾浓度降低以及升高时，36Cl外流均增加。4. 计算得出的钾的渗透系数（PK）在5 - 4 mM - K时最大，在较高钾浓度时略有下降，但在无钾溶液中显著下降（降至5 - 4 mM - K时值的约1/5）。在无氯介质中，PK降至氯介质中值的0 - 67，与钾浓度无关。5. 计算得出的PCl在无钾和16 - 2 mM - K时比在5 - 4 mM - K时更大。6. PK/PCl比值随细胞外钾浓度的变化呈现重要变化：在5 - 4 mM - K时该值为5，在16 - 2 mM - K和无钾溶液中分别降至2和0 - 5。7. 结果表明，在无氯介质中通过电学方法测量的膜电阻变化的部分原因是钾电导同时降低。
