Nagai I, Oota I, Nagai T
Jpn J Physiol. 1979;29(1):61-73. doi: 10.2170/jjphysiol.29.61.
The effect of SCN on potassium contracture, especially the time course and the mechanical inactivation of the contracture, was investigated using frog twitch muscle fibers. SCN increased the magnitude and the rate of rise of the potassium contracture tension and prolonged its time course. These effects of SCN depended on the concentration of K+ in the external medium and on the duration of pretreatment of the fibers with SCN-Ringer solution. The potentiating effect of SCN on the potassium contracture tension was pronounced at lower and moderate concentrations of K+ and this effect attained a maximum within 1 min after the pretreatment. In the contracture induced by exposure of the fibers to K-SCN-solution without the pretreatment, the time course of the contracture, especially the retardation of the spontaneous relaxation, was marked at higher concentrations of K+. This retarding effect of SCN attained a maximum at more than 10 min after the pretreatment with SCN-Ringer solution. SCN shifted the mechanical inactivation curve of potassium contracture toward lower concentrations of K+, as in the case of the activation curve, and markedly increased the rate of the inactivation induced by conditioning with 15 mM K+. In addition, SCN delayed the recovery of potassium contracture from the mechanical inactivation induced by preceding K-SCN-contracture. On the basis of these results, the sites and the mechanism of action of SCN on potassium contracture are discussed.
利用青蛙的单收缩肌纤维研究了硫氰酸盐（SCN）对钾挛缩的影响，特别是挛缩的时间进程和机械失活。SCN增加了钾挛缩张力的幅度和上升速率，并延长了其时间进程。SCN的这些作用取决于细胞外液中钾离子（K+）的浓度以及用含SCN的任氏液对纤维进行预处理的持续时间。在较低和中等浓度的K+条件下，SCN对钾挛缩张力的增强作用较为明显，且在预处理后1分钟内这种作用达到最大值。在未进行预处理而将纤维暴露于K-SCN溶液所诱导的挛缩中，挛缩的时间进程，尤其是自发松弛的延迟，在较高浓度的K+条件下较为明显。在用含SCN的任氏液预处理后10分钟以上，SCN的这种延迟作用达到最大值。与激活曲线的情况一样，SCN将钾挛缩的机械失活曲线向较低浓度的K+方向移动，并显著增加了用15 mM K+预处理所诱导的失活速率。此外，SCN延迟了钾挛缩从先前K-SCN挛缩所诱导的机械失活中的恢复。基于这些结果，对SCN在钾挛缩上的作用位点和作用机制进行了讨论。
