Schilling W P, Schuil D W, Bagwell E E, Lindenmayer G E
J Membr Biol. 1984;77(2):101-14. doi: 10.1007/BF01925860.
Vesicles in a highly enriched sarcolemma preparation from canine ventricle were found to develop membrane potentials in response to outwardly directed potassium and inwardly directed sodium concentration gradients. The magnitude of the potential measured by the fluorescent dye diS-C3-(5) suggested a sodium-to-potassium permeability ratio between 0.2 and 1.0 which is one to two orders of magnitude greater than values obtained for the myocardial cell. Radiotracer techniques were employed to evaluate the permeability coefficients of the isolated cardiac sarcolemma membrane for sodium and potassium under equilibrium conditions (i.e., equal salt concentrations in the intravesicular and extravesicular spaces). The uptake of sodium and potassium was best described by two exponential processes which followed an increment of uptake that occurred prior to the earliest assay time (i.e., 17 sec). The compartment sizes were linear, nonsaturable functions of the cation activity. Evaluation of the rate coefficients of cation uptake by the two exponential processes versus cation activity revealed that sodium influx via the slow process and potassium influx via the fast process varied linearly with cation activity, suggesting that the permeability coefficients were concentration independent for these compartments. Conversely, sodium influx via the fast process exhibited a nonlinear increase with increasing sodium activity, and potassium influx via the slow process appeared to saturate with increasing potassium activity. In general, the permeabilities of the sarcolemma-enriched preparation for sodium and potassium were of equal magnitude. The permeability coefficients were lower than that for the potassium coefficient reported for cardiac cells but are in the range of that reported for sodium.
在犬心室高度富集的肌膜制剂中发现，囊泡会响应外向钾离子浓度梯度和内向钠离子浓度梯度产生膜电位。用荧光染料二硫氰基甲烷（diS-C3-(5)）测量的电位大小表明，钠钾通透性比在0.2到1.0之间，这比心肌细胞获得的值大1到2个数量级。采用放射性示踪技术评估在平衡条件下（即囊泡内和囊泡外空间盐浓度相等）分离的心肌肌膜对钠和钾的通透性系数。钠和钾的摄取最好用两个指数过程来描述，这两个过程遵循在最早测定时间（即17秒）之前发生的摄取增量。隔室大小是阳离子活性的线性、非饱和函数。通过两个指数过程对阳离子摄取速率系数与阳离子活性的评估表明，通过慢过程的钠内流和通过快过程的钾内流随阳离子活性呈线性变化，这表明这些隔室的通透性系数与浓度无关。相反，通过快过程的钠内流随钠活性增加呈非线性增加，通过慢过程的钾内流似乎随钾活性增加而饱和。一般来说，富含肌膜的制剂对钠和钾的通透性大小相等。通透性系数低于报道的心肌细胞钾系数，但在报道的钠系数范围内。
