Lewartowski B, Pytkowski B, Janczewski A
Pflugers Arch. 1984 Jun;401(2):198-203. doi: 10.1007/BF00583882.
Ca shifts in the isolated, perfused ventricular muscle of guinea-pig hearts were investigated with the aid of 45Ca under the conditions of complete equilibration of preparations with the isotope-containing solution. In some series of experiments total Ca content was also measured by means of atomic absorption spectrophotometry. The content of 45Ca at the end of 70 min equilibration period during which the ventricles were stimulated at a rate of 60/min was 1.66 +/- 0.09 mmol/kg w.w. This content dropped to 0.42 +/- 0.09 mmol/kg w.w. within 4 min of rest. Contractile force also decreased to 21% of control. Both the content of 45Ca and contractile force returned to the pre-rest values within the 4 min of post-rest stimulation. The difference between the total Ca content in the rested and stimulated muscle was comparable to the respective difference in 45Ca contents. A significant linear correlation between this 45Ca fraction which was lost at rest and recovered during the post-rest stimulation, and contractile force was found under the following experimental conditions: I. post-rest recovery, II. decay during rest, III. post-rest stimulation at various rates. These results are consistent with the hypothesis proposing that this Ca fraction is involved in the frequency-dependent control of contractile force.
在豚鼠心脏的离体灌注心室肌中，借助 (^{45}Ca) 在制剂与含同位素溶液完全平衡的条件下研究了钙的转移。在一些系列实验中，还通过原子吸收分光光度法测量了总钙含量。在以 (60次/分钟) 的频率刺激心室的 (70) 分钟平衡期结束时，(^{45}Ca) 含量为 (1.66\pm0.09 mmol/kg) 湿重。在休息 (4) 分钟内，该含量降至 (0.42\pm0.09 mmol/kg) 湿重。收缩力也降至对照值的 (21%)。在休息后刺激的 (4) 分钟内，(^{45}Ca) 含量和收缩力均恢复到休息前的值。休息和刺激状态下肌肉的总钙含量差异与 (^{45}Ca) 含量的相应差异相当。在以下实验条件下发现，休息时丢失并在休息后刺激期间恢复的该部分 (^{45}Ca) 与收缩力之间存在显著的线性相关性：I. 休息后恢复；II. 休息期间衰减；III. 以不同频率进行休息后刺激。这些结果与提出该部分钙参与收缩力频率依赖性控制的假设一致。
