论文部分内容阅读
目的探讨犬心房颤动(房颤)时T型钙通道在心房电重塑中的作用及机制。方法将2002年2月至2006年10月北京大学人民医院动物实验的杂种犬15条,分为3组,每组5条,分别为正常对照组、单纯房颤组和房颤+mibefradil组。房颤组在右心房植入起搏器进行快速起搏建立犬慢性房颤模型;房颤+T型钙通道阻滞剂mibefradil组在起搏术后第2天开始给mibefradil(术后稳定24h)。正常对照组不植入起搏器。采用电生理检查方法测定房颤的持续时间和心房有效不应期;胶原酶Ⅱ型分离心房肌细胞,激光共聚焦显微镜检测Ca2+通道阻滞剂对细胞内Ca2+浓度变化的影响。结果(1)术前的心房有效不应期为280/90~110ms。起搏24周时,房颤+mibefradil组的心房有效不应期延长为2000/1400~1700ms。起搏24周时单纯房颤组中有75%的犬呈自身持续性房颤,而房颤+mibefradil组有20%呈持续性房颤,其余犬在给予短阵猝发刺激(500/min)时可诱发出房颤,持续时间为1~6min。(2)正常对照组的心房肌细胞在阻滞L型Ca2+通道后细胞内Ca2+浓度没有明显改变(1.17±0.09OD比值),单纯房颤组在阻滞L型Ca2+通道后细胞内Ca2+浓度明显升高(2.35±1.05OD比值),与正常对照组比较差异有显著性意义(P<0.05),而房颤+mibefradil组在阻滞L型Ca2+通道后细胞内Ca2+浓度比单纯房颤组下降30%(2.05±0.90OD比值)。(3)正常对照组、单纯心房颤动组和房颤+mibefradil组的心房肌细胞在阻滞T型Ca2+通道后细胞内Ca2+浓度均增高(1.49±0.17,1.53±0.33和1.38±0.35OD比值),且3组间比较差异均无显著性意义。结论(1)T型Ca2+通道阻滞剂能够明显延长房颤时的心房有效不应期,并能缩短房颤的持续时间,但并不能阻止房颤的发生;(2)房颤时心房肌细胞的T型Ca2+电流增加,而L型Ca2+电流减少,提示T型Ca2+通道可能在房颤时的心房肌细胞内Ca2+超载机制中起主要作用。
Objective To investigate the role and mechanism of T-type calcium channel in atrial remodeling in canine atrial fibrillation (AF). Methods From February 2002 to October 2006 Peking University People ’s Hospital animal experiment 15 dogs were divided into 3 groups of 5, respectively, the normal control group, atrial fibrillation group and atrial fibrillation + mibefradil group. Atrial fibrillation group was implanted in the right atrium for rapid pacing to establish canine chronic atrial fibrillation model; atrial fibrillation + T-type calcium channel blocker mibefradil group started on day 2 after pacing to mibefradil (postoperative 24h ). Normal control group did not implanted pacemaker. The electrophysiological examination was used to determine the duration of atrial fibrillation and the effective refractory period of atrial fibrinolysis. The atrial fibrinogen was isolated by collagenase Ⅱ and the effect of Ca2 + channel blocker on the intracellular Ca2 + concentration was measured by confocal microscopy. Results (1) Preoperative atrial effective refractory period was 280/90 ~ 110ms. At 24 weeks of pacing, the atrial effective refractory period in patients with atrial fibrillation + mibefradil was prolonged to 2000/1400 to 1700 ms. At 24 weeks of pacing, 75% of dogs in the atrial fibrillation group had persistent AF, whereas 20% of patients in the atrial fibrillation + mibefradil group had sustained AF, while the remaining dogs were given burst stimulation (500 / min) Atrial fibrillation can be induced when the duration of 1 ~ 6min. (2) There was no significant change in intracellular Ca2 + concentration (1.17 ± 0.09 OD ratio) in normal control group atrial fibrillation cells after blocking L-type Ca2 + channels, intracellular Ca2 + concentration was significantly increased in L-type Ca2 + channels (2.35 ± 1.05OD), there was significant difference compared with normal control group (P <0.05), while the intracellular Ca2 + concentration in L-type Ca2 + channel in atrial fibrillation + mibefradil group was lower than that in atrial fibrillation group 30% (2.05 ± 0.90 OD ratio). (3) The intracellular Ca2 + concentrations of the atrial myocytes in the normal control group, the atrial fibrillation group and the atrial fibrillation + mibefradil group were both higher than those in the atrial fibrillation + mibefradil group (1.49 ± 0.17,1.53 ± 0.33 and 1.38 ± 0.35OD) , And no significant difference between the three groups. Conclusion (1) T-type Ca2 + channel blockers can significantly prolong atrial refractory period of atrial fibrillation, and can shorten the duration of atrial fibrillation, but does not prevent the occurrence of atrial fibrillation; (2) atrial fibrillation T-type Ca2 + currents increased, while L-type Ca2 + currents decreased, suggesting that T-type Ca2 + channels may play a major role in the mechanism of Ca2 + overload in atrial myocytes.