BACKGROUND The potential mechanism of mepivacaine's myocardial depressant effect observed in papillary muscle has not yet been investigated at cellular level. Therefore, we evaluated mepivacaine's effects on Ca2+ transient in isolated adult mouse cardiomyocytes. METHODS Single ventricular myocytes were enzymatically isolated from wild-type C57Bl/6 mice and loaded with 10 μM fluorescent Ca2+ indicator Fluo-4-AM to record intracellular Ca2+ transients upon electrical stimulation. The mepivacaine effects at half-maximal inhibitory concentration (IC50) was determined on calibrated cardiomyocytes' Ca2+ transients by non-parametric statistical analyses on biophysical parameters. Combination of mepivacaine with NCX blockers ORM-10103 or NiCl2 were used to test a possible mechanism to explain mepivacaine-induced Ca2+ transients' reduction. RESULTS A significant inhibition at mepivacaine's IC50 (50 μM) on Ca2+ transients was measured in biophysical parameters such as peak (control: 528.6 ± 73.61 nM vs mepivacaine: 130.9 ± 15.63 nM; p < 0.05), peak area (control: 401.7 ± 63.09 nM*s vs mepivacaine: 72.14 ± 10.46 nM*s; p < 0.05), slope (control: 7699 ± 1110 nM/s vs mepivacaine: 1686 ± 226.6 nM/s; p < 0.05), time to peak (control: 107.9 ± 8.967 ms vs mepivacaine: 83.61 ± 7.650 ms; p < 0.05) and D50 (control: 457.1 ± 47.16 ms vs mepivacaine: 284.5 ± 22.71 ms; p < 0.05). Combination of mepivacaine with NCX blockers ORM-10103 or NiCl2 showed a significant increase in the baseline of [Ca2+] and arrhythmic activity upon electrical stimulation. CONCLUSION At cellular level, mepivacaine blocks Na+ channels, enhancing the reverse mode activity of NCX, leading to a significant reduction of Ca2+ transients. These results suggest a new mechanism for the mepivacaine-reduction contractility effect.

中文翻译：

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甲哌卡因可减少离体鼠心室心肌细胞的钙瞬变。

背景技术尚未在细胞水平上研究在乳头肌中观察到的甲哌卡因对心肌的抑制作用的潜在机制。因此，我们评估了米吡卡因对离体成年小鼠心肌细胞中Ca2 +瞬变的影响。方法从野生型C57Bl / 6小鼠中酶分离单心室心肌细胞，并加载10μM荧光Ca2 +指示剂Fluo-4-AM，以记录电刺激后的细胞内Ca2 +瞬变。通过对生物物理参数的非参数统计分析，确定了半数最大抑制浓度（IC50）时的甲哌卡因对校准的心肌细胞Ca2 +瞬变的影响。甲哌卡因与NCX阻滞剂的组合使用ORM-10103或NiCl2来测试可能的机制来解释甲哌卡因引起的Ca2 +瞬变的减少。结果在生物物理参数（例如峰（对照：528.6±73.61 nM）与哌哌卡因：130.9±15.63 nM； p <0.05），峰面积（对照：401.7±63.09）之间，测量了甲哌卡因的IC50（50μM）对Ca2 +瞬变具有显着抑制作用。 nM * s与甲哌卡因：72.14±10.46 nM * s; p <0.05），斜率（对照：7699±1110 nM / s与甲哌卡因：1686±226.6 nM / s; p <0.05），达到峰值的时间（对照：107.9）对米比卡因为±8.967 ms：83.61±7.650 ms; p <0.05）和D50（对照：对米比卡因为457.1±47.16 ms：284.5±22.71 ms; p <0.05）甲哌卡因与NCX阻滞剂ORM-10103或NiCl2的组合显示，[Ca2 +]基线和电刺激后的心律不齐活动显着增加。结论在细胞水平上，甲哌卡因会阻断Na +通道，从而增强NCX的反向模式活性，导致Ca2 +瞬变的显着减少。这些结果提示了一种新的机制，可降低甲哌卡因的收缩作用。