Piwnica-Worms D, Jacob R, Horres C R, Lieberman M
J Gen Physiol. 1983 May;81(5):731-48. doi: 10.1085/jgp.81.5.731.
To evaluate the transmembrane movement of chloride in a preparation of cardiac muscle lacking the extracellular diffusion limitations of natural specimens, intracellular chloride concentration ( [Cl] i) and transmembrane 36Cl efflux have been determined in growth-oriented embryonic chick heart cells in tissue culture. Using the method of isotopic equilibrium, [Cl]i was 25.1 +/- 7.3 mmol x (liter cell water)-1, comparable to the value of 24.9 +/- 5.4 mmol x (liter cell water)-1 determined by coulometric titration. Two cellular 36Cl compartments were found; one exchanged with a rate constant of 0.67 +/- 0.12 min-1 and was associated with the cardiac muscle cells; the other, attributed to the fibroblasts, exchanged with a rate constant of 0.18 +/- 0.05 min-1. At 37 degrees C, transmembrane Cl flux of cardiac muscle under steady-state conditions was 30 pmol x cm-2 x s-1. In K-free, normal, or high-Ko solutions, the responses of the membrane potential to changes in external Cl concentration suggested that chloride conductance was low. These results indicate that Cl transport across the myocardial cell membrane is more rapid than K transport and is largely electrically silent.
为了在不存在天然标本细胞外扩散限制的心肌制备物中评估氯离子的跨膜运动，我们测定了组织培养中生长取向的胚胎鸡心脏细胞的细胞内氯离子浓度（[Cl]i）和跨膜36Cl外流。使用同位素平衡法，[Cl]i为25.1±7.3 mmol·(升细胞水)-1，与库仑滴定法测定的24.9±5.4 mmol·(升细胞水)-1的值相当。发现了两个细胞36Cl区室；一个以0.67±0.12 min-1的速率常数进行交换，与心肌细胞相关；另一个归因于成纤维细胞，以0.18±0.05 min-1的速率常数进行交换。在37℃时，稳态条件下心肌的跨膜Cl通量为30 pmol·cm-2·s-1。在无钾、正常或高钾o溶液中，膜电位对外部Cl浓度变化的反应表明氯离子电导较低。这些结果表明，Cl跨心肌细胞膜的转运比K转运更快，并且在很大程度上是电沉默的。
