CALCIUM CURRENT AND TENSION GENERATION IN IMMATURE MAMMALIAN MYOCARDIUM - EFFECTS OF DILTIAZEM
CALCIUM CURRENT AND TENSION GENERATION IN IMMATURE MAMMALIAN MYOCARDIUM - EFFECTS OF DILTIAZEM
复制标题
DOI：
10.1016/0022-2828(91)90214-7
复制
发表时间：
1991-07-01
影响因子：
5
通讯作者：
FRIEDMAN, WF
中科院分区：
文献类型：
--
作者：
KLITZNER, TS;CHEN, FH;FRIEDMAN, WF
采用单蔗糖间隙和离体心肌细胞电压钳技术研究地尔硫卓对新生新西兰白兔离体心室肌细胞和右心室乳头肌钙电流（ICa）和张力产生的影响。地尔硫卓可显着缩短离体心肌细胞动作电位的持续时间，而对超调电位或静息膜电位没有影响。地尔硫卓阻断但没有完全消除这些新生细胞中的ICa。在沐浴乳头肌的溶液中添加地尔硫卓导致动作电位持续时间类似的减少，同时伴随着抽搐张力的减少。当使用单蔗糖间隙电压钳控制去极化的持续时间时，尽管相同肌肉的抽搐张力显着降低，但地尔硫卓引起的张力发展的降低被消除。在另一系列实验中，表明新生儿乳头肌张力的大小取决于去极化的持续时间。总而言之，这项研究的结果表明，在新生儿心肌中，当ICai被地尔硫卓阻断时，所导致的张力降低部分是由于动作电位持续时间的减少引起的。由IC携带到新生儿心脏细胞中的钙似乎并不是兴奋-收缩耦合的细胞外Ca2+的唯一来源。最后，动作电位似乎充当钙移动到新生儿心脏细胞的大门。
Single sucrose gap and isolated myocyte voltage-clamp techniques were used to study the effects of diltiazem on calcium current (ICa) and tension generation in isolated ventricular myocytes and right ventricular papillary muscles from neonatal New Zealand White rabbits. Diltiazem was shown to significantly shorten the duration of isolated myocyte action potentials with no effect on overshoot potential or resting membrane potential. Diltiazem blocked but did not completely abolishICain these neonatal cells. Addition of diltiazem to the solution bathing papillary muscles resulted in a similar reduction in action potential duration accompanied by a reduction in twitch tension. When the duration of depolarization was controlled employing the single sucrose gap voltage clamp, the decrease in tension development caused by diltiazem was abolished despite a significant decrease in twitch tension in the same muscles. In another series of experiments it was demonstrated that the magnitude of developed tension in neonatal papillary muscles is dependent upon the duration of depolarization. Taken together, the results of this investigation suggest that in neonatal myocardium whenICais blocked by diltiazem, the resulting reduction in developed tension is caused in part by reduction of action potential duration. The calcium carried into the neonatal heart cell byICadoes not appear to be the only source of extracellular Ca2+for excitation-contraction coupling. Finally, the action potential appears to act as a gate for calcium movement into the neonatal heart cell.