Fortier P A, Bedford G K, Chiong M A
Can J Physiol Pharmacol. 1985 Nov;63(11):1429-34. doi: 10.1139/y85-235.
We tested the hypothesis that the myocardial effects of verapamil (VER) could be enhanced by decreasing the extracellular Ca2+ concentration ([Ca2+]o) in the isolated rabbit heart at 37 degrees C. After perfusion with standard Krebs - bicarbonate solution containing 1.27 mM Ca2+, for a 30-min period of stabilization and 15 min of control, groups of hearts were perfused for an additional 60 min with solutions containing one of the following: 1.27 mM Ca2+ (control group), 0.23 mM Ca2+ (low [Ca2+]o group), 1.27 mM Ca2+ plus 10(-7) M VER (VER group), or 0.23 mM Ca2+ plus 10(-7) M VER (combination, CBN group). These concentrations of [Ca2+]o and VER produce submaximal responses in our preparation. We found that the heart rate - LV pressure product (RPP) in the CBN group fell rapidly to 0 in the first 2-3 min of perfusion, this response being significantly lower than in the other two groups for the first 15 min. Electromechanical dissociation (EMD) appeared in one of six hearts at 60 min and in four of six hearts at 30 min in the low [Ca2+]o and VER groups, respectively, whereas it occurred in the CBN group in all hearts at 3 min. Depolarization rate (DR) fell by 10% in the low [Ca2+]o and VER groups versus a reduction of 45% in the CBN group (P less than 0.05) during the last 45 min of perfusion. The PR interval increased by 300% in the CBN group, a much greater and significant change (P less than 0.05) than in the hearts exposed to VER or low [Ca2+]o.(ABSTRACT TRUNCATED AT 250 WORDS)
在37摄氏度的离体兔心脏中，通过降低细胞外钙离子浓度（[Ca2+]o）可以增强维拉帕米（VER）对心肌的作用。在用含1.27 mM钙离子的标准 Krebs - 碳酸氢盐溶液灌注30分钟以实现稳定状态以及15分钟作为对照后，将心脏分组，再用含有以下成分之一的溶液额外灌注60分钟：1.27 mM钙离子（对照组）、0.23 mM钙离子（低[Ca2+]o组）、1.27 mM钙离子加10(-7) M VER（VER组）或0.23 mM钙离子加10(-7) M VER（联合组，CBN组）。这些[Ca2+]o和VER的浓度在我们的实验制剂中产生次最大反应。我们发现，CBN组的心率 - 左心室压力乘积（RPP）在灌注的前2 - 3分钟内迅速降至0，在前15分钟内该反应显著低于其他两组。在低[Ca2+]o组和VER组中，分别有1/6的心脏在60分钟时以及4/6的心脏在30分钟时出现电机械分离（EMD），而在CBN组中，所有心脏在3分钟时就出现了EMD。在灌注的最后45分钟内，低[Ca2+]o组和VER组的去极化速率（DR）下降了10%，而CBN组下降了45%（P < 0.05）。CBN组的PR间期增加了300%，这一变化比暴露于VER或低[Ca2+]o的心脏中更大且更显著（P < 0.05）。（摘要截断于250字）
