Hermsmeyer K, Rulon R, Sperelakis N
J Gen Physiol. 1972 Jun;59(6):779-93. doi: 10.1085/jgp.59.6.779.
The effect of hypertonicity on the electrical properties of vertebrate myocardial cells was studied in ventricular muscle fibers of guinea pig, cat, frog, and chicken. The latter two species do not have a T-tubule system, whereas the former two do. In hypertonic solutions (2 x isotonic) produced by addition of sucrose or excess of NaCl, cell diameter decreased and there was a slight hyperpolarization and decrease in action potential overshoot. In guinea pig and cat, the hypertonic solution caused a decrease in input resistance and the plateau of the action potential to disappear in some of the cells; contractions of the entire ventricle also became depressed. These effects were reversed by returning the muscle fibers to isotonic solution. Addition of 5 mM SrCl(2) to the hypertonic solution also caused the plateau component and contraction to reappear. In frog and chick cells, loss of the plateau component and contraction never occurred in hypertonic solution, and input resistance increased. Urea and glycerol hyperosmolarity (2 x) caused no loss of the plateau component or contraction. If the frog and chicken ventricular, and guinea pig atrial myocardial cells (all of which lack T tubules) were to serve as an adequate control for possible effects of hypertonicity on the surface membrane and on contractile proteins, then the results suggest that swelling of the T tubules of mammalian myocardial cells leads to loss of the plateau component.
在豚鼠、猫、青蛙和鸡的心室肌纤维中研究了高渗对脊椎动物心肌细胞电特性的影响。后两种动物没有T管系统，而前两种有。在通过添加蔗糖或过量氯化钠产生的高渗溶液（2倍等渗）中，细胞直径减小，动作电位有轻微超极化且超射减小。在豚鼠和猫中，高渗溶液导致输入电阻降低，并且在一些细胞中动作电位的平台期消失；整个心室的收缩也变得减弱。将肌纤维恢复到等渗溶液后，这些效应会逆转。向高渗溶液中添加5 mM SrCl₂也会使平台期成分和收缩重新出现。在青蛙和鸡的细胞中，高渗溶液中从未出现平台期成分和收缩的丧失，并且输入电阻增加。尿素和甘油高渗（2倍）不会导致平台期成分或收缩的丧失。如果青蛙和鸡的心室以及豚鼠的心房心肌细胞（所有这些都缺乏T管）能够作为高渗对表面膜和收缩蛋白可能影响的适当对照，那么结果表明哺乳动物心肌细胞T管的肿胀会导致平台期成分的丧失。
