双苯氟嗪对豚鼠心室肌细胞膜钠电流的影响(英文)

Effect of dipfluzine on sodium current in guinea-pig ventricular myocytes

目的观察双苯氟嗪对豚鼠心室肌细胞膜钠电流的影响。方法用酶解方法分离豚鼠心室肌细胞,全细胞膜片钳技术记录钠电流。结果将细胞钳制在-80mV,给(-80～+50)mV,50ms和步阶10mV的去极化脉冲,记录到的电流被河豚毒素10μmol·L-1完全抑制。在该刺激条件下,该电流最大激活电压在-20mV左右,翻转电压在+30mV左右,提示该电流为钠电流。双苯氟嗪可以浓度依赖性地抑制钠电流。双苯氟嗪对钠电流的抑制作用在冲洗后可部分恢复,表明其对钠通道的抑制作用具有可逆性。双苯氟嗪可使钠电流I-V曲线上移,但对钠电流的电压依赖性特征、最大激活电压和翻转电压无明显影响。在双苯氟嗪40μmol·L-1存在下,最大激活电压下的峰值电流下降约46%;双苯氟嗪可明显使钠电流稳态失活曲线左移,但不影响曲线的斜率因子。双苯氟嗪40μmol·L-1可使钠电流半数失活电压从(-73.0±4.6)mV减少到(-82.8±7.2)mV。但双苯氟嗪对钠电流稳态激活无明显影响,在双苯氟嗪40μmol·L-1存在下,半数激活电压(-33.7±3.6)mV和斜率因子(5.6±2.4)mV与对照组激活电压(-34.9±5.1)mV和斜率因子(6.0±4.8)mV相比无显著性差异。双苯氟嗪可以使钠电流从失活状态下恢复明显减慢,双苯氟嗪40μmo·lL-1可使恢复时间常数延长(79±28)vs(36±11)ms。结论双苯氟嗪可以浓度依赖性、使用依赖性和频率依赖性地抑制心肌钠电流,并且主要作用于钠电流的失活状态。

AIM To investigate effect of dipfluzine on sodium current （INa＋ ） in isolated single guinea-pig ventricular myocytes. METHODS INa＋ was meas- ured by whole cell patch-clamp technique in single iso- lated guinea-pig ventricular myocytes which were pre- pared by enzymatic dissociation method. RESULTS Cardiac INa＋ was elicited by 50-ms pulses to ＋ 50 mV from holding potential at -80 mV with a step of ＋ 10 mV, which could be blocked completely by tetro- dotoxin 10 μmol·L-1. The peak INa ＋ occurred at about -20 mV and the reversal potential for INa ＋ was about ＋30 inV. Dipfluzine inhibited cardiac INa＋ in a con- centration-dependent manner. The blocking effect of dipfluzine on INa＋ was reversible. Dipfluzine sup- pressed cardiac INa＋, without modifying maximum activation potential and reversal potential. The peak of INa＋ was decreased by about 46% at -20 mV and shape of I-V curve was not ahered by dipfluzine 40 μmol·L-l. Dipfluzine shifted the steady-state inactiva- tion curve of INa ＋ towards more negative without chan- ging the slope factor and produced very little change in the steady-state activation curve towards more positive. The mean half activation voltage was （ - 34.9± 5.1 ） mV and slope factor was （6.0 ± 4.8 ） mV under con- trol condition and （ -33.7 ±3.6） mV and （5.6± 2.4） mV following exposure to dipfluzine 40 μmol· L- 1. The half inactivation voltage was （ - 73.0 ± 4.6 ） mV and slope factor was （4.8 ± 1.8 ） mV under control condition and （ -82.8±7.2）mV and （4.8±1.8） mV following dipfluzine 40 μmol· L-1 treatment. Dip- fluzine delayed recovery of cardiac INa ＋ from inactivation state. The time course of recovery was （36± 11 ） ms in control group and （ 79 ± 28 ） ms in dipfluzine 40 μmol· L-1 group. CONCLUSION Dipfluzine inhi- bits cardiac INa＋ in a concentration-dependent manner and has higher affinity for the inactivated state than that for resting state of Na ＋ channels.