Wohlfart B, Khan A R
Acta Physiol Scand. 1987 Jun;130(2):187-91. doi: 10.1111/j.1748-1716.1987.tb08127.x.
The inotropic effects of prenalterol were studied in papillary muscles isolated from the right ventricle of guinea-pig hearts. Force production and action potential were recorded. The preparations were paced at 0.4 Hz (at 31-32 degrees C) under isometric conditions. Prenalterol, in concentration 0.1 microM did not change the action potential duration whereas the peak force and the maximum rate of force development increased by 40.3 and 36.3%, respectively. Time to peak force was slightly shortened (-3.0%) and so was the time from peak force to half relaxation (-5.2%). A predetermined stimulus protocol was used for assessment of the recirculation fraction of activator calcium. At selected times an extra contraction was introduced in order to obtain contractile potentiation. Force of the subsequent two test contractions (after fixed intervals) was analysed. Prenalterol slightly reduced the decay of the postextrasystolic potentiation measured in the two test contractions. It is suggested that the inotropic effect of prenalterol is due to an intensified calcium influx during the action potential, and to some extent to more efficient re-utilization of released calcium. There seems to be a more rapid release of calcium from troponin C giving rise to a shortened time to peak force and an enhanced relaxation.
在从豚鼠心脏右心室分离出的乳头肌中研究了普瑞特罗的变力作用。记录了力的产生和动作电位。在等容条件下，将标本以0.4Hz的频率（在31 - 32摄氏度）进行起搏。浓度为0.1微摩尔的普瑞特罗并未改变动作电位持续时间，而峰值力和力发展的最大速率分别增加了40.3%和36.3%。达到峰值力的时间略有缩短（-3.0%），从峰值力到半松弛的时间也是如此（-5.2%）。使用预定的刺激方案来评估激活钙的再循环分数。在选定的时间引入一次额外收缩以获得收缩增强。分析随后两次测试收缩（在固定间隔后）的力。普瑞特罗略微降低了在两次测试收缩中测量的早搏后增强的衰减。提示普瑞特罗的变力作用是由于动作电位期间钙内流增强，并且在一定程度上是由于释放钙的再利用更有效。似乎存在从肌钙蛋白C更快地释放钙，导致达到峰值力的时间缩短和舒张增强。
