Prokopczuk A
Department of Clinical Physiology, Medical Centre of Postgraduate Education, Warsaw.
Acta Physiol Pol. 1987 Nov-Dec;38(6):506-15.
Calcium shifts accompanying rest and post-rest phenomena in isolated left atrial appendages of guinea-pig heart were investigated by means of isotope 45Ca2+. Experiments were performed under conditions of full equilibration of preparations with isotope-containing solution (at least 45 min) in order to investigate the changes in content of exchangeable Ca, or at short exposure to isotope (2-5 min) in order to measure the excitation-dependent Ca2+ influx. Atria stimulated at the rate of 60/min for 55 min in radioactive solution contained 3.79 +/- 0.21 mM of 45Ca2+/kg of wet weight (w.w.). The rested preparations contained 2.61 +/- 0.23 mM/kg w.w. When the previously stimulated for 45 min atria were allowed to rest for 10 min, their content of 45Ca2+ dropped to 3.01 +/- 0.17 mM/kg w.w. despite continued exposure to this isotope. The first post-rest contraction was by 50% +/- 25% stronger than the control steady-state beats. Contractile force (CF) decreased during the two following beats to 25% of control. Calcium-45 content dropped during these beats to 2.50 +/- 0.14 mM/kg w.w. whereas influx of 45Ca2+ amounted to 0.24 mM/kg w.w. CF recovered to control values during 10 min of the following stimulation. Calcium-45 content reached at this time 4.09 +/- 0.12 mM/kg w.w. It is proposed that there are two intracellular store compartments in guinea-pig atrial muscle. The capacity of one of them is rate-dependent and its Ca2+ is lost at rest. This Ca2+ is partially trapped by the other compartment (presumably sarcoplasmic reticulum) and is released to activate the strong post-rest contraction.
利用同位素(^{45}Ca^{2 + })研究了豚鼠心脏离体左心耳在静息和静息后现象时的钙转移情况。实验在制剂与含同位素溶液充分平衡（至少(45)分钟）的条件下进行，以研究可交换钙含量的变化；或在短时间暴露于同位素（(2 - 5)分钟）的条件下进行，以测量兴奋依赖性(Ca^{2 + })内流。在放射性溶液中以(60)次/分钟的频率刺激心房(55)分钟后，每千克湿重含(3.79 ± 0.21)毫摩尔的(^{45}Ca^{2 + })。静息制剂每千克湿重含(2.61 ± 0.23)毫摩尔。当先前刺激(45)分钟的心房静息(10)分钟时，尽管持续暴露于该同位素，其(^{45}Ca^{2 + })含量降至(3.01 ± 0.17)毫摩尔/千克湿重。静息后的第一次收缩比对照稳态搏动强(50% ± 25%)。在随后的两次搏动中，收缩力（CF）降至对照的(25%)。在这些搏动期间，(^{45}Ca)含量降至(2.50 ± 0.14)毫摩尔/千克湿重，而(^{45}Ca^{2 + })内流为(0.24)毫摩尔/千克湿重。在随后(10)分钟的刺激过程中，CF恢复到对照值。此时(^{45}Ca)含量达到(4.09 ± 0.12)毫摩尔/千克湿重。有人提出豚鼠心房肌中有两个细胞内储存区室。其中一个的容量与速率有关，其(Ca^{2 + })在静息时丢失。这种(Ca^{2 + })部分被另一个区室（可能是肌浆网）捕获并释放，以激活强烈的静息后收缩。
