哇巴因对家兔左心房后壁动作电位和L型钙电流的影响

目的探讨哇巴因对家兔左心房后壁(LAPW)和左心耳底部(LAA)心肌细胞动作电位和L型钙电流(I_(Ca-L))的影响。方法酶解法分离家兔的LAPW和LAA组织的心肌细胞。全细胞膜片钳技术记录各个部位心肌细胞动作电位和I_(Ca-L)的变化。结果在电流钳制下,LAPW的动作电位时程复极比50%(APD_(50))和动作电位时程复极比90%(APD_(90))明显长于LAA的APD_(50)和APD_(90)(均为P<0.05)。哇巴因(1μmol/L)使LAPw和LAA心肌细胞动作电位形态呈三角形尖锥峰形,APD_(50)和APD_(90),以及静息电位和动作电位幅值幅度均明显短于各自的对照组(均为P<0.01);LAPW心肌细胞APD_(50)和APD_(90)还明显短于LAA心肌细胞加药前后的APD_(50)和APD_(90)(均为P<0.05)。在电压钳制方式下,正常组LAPW的I_(Ca-L)的电流密度明显小于LAA的I_(Ca-L)的电流密度(P<0.05)。但在1μmoL/L哇巴因作用下,它们各自I_(Ca-L)的幅度有明显增加,LAPW的I_(Ca-L)最大电流密度为(-11.13±0.99)pA/pF,LAA的I_(Ca-L)为(-8.86±0.51)pA/pF(P<0.01)。在对照组中,LAPW的I_(Ca-L)的I-V曲线位于最底部,经哇巴因作用后,LAPW的I_(Ca-L)的I-V曲线上移到其他I-V曲线的最上部。结论家兔LAPW和LAA心肌细胞存在离子流特异性差异,哇巴因加重LAPW和LAA的离子流大小异质性和离子电流的重新分配,这可能成为心房颤动易发性的启动因素和维持条件。

Effects of ouabian on action potentials and L-type calcium current of left atrial posterior wall in rabbits

Objective To investigate the effects of ouabain on action potential and L-type calcium current （ICa-L） of left atrial posterior wall （LAPW）and left atrial appendage tissue （LAA）in rabbit myocytes. Methods Atrial myocytes of LAPWs and LAAs of rabbits were obtained by enzymatic dissociation. The whole-cell patch-clamp technique was used to assess the effects of ouabain on action potential （AP） and Ica-L. Results According to current clamp protocol, APs recorded in LAPW and LAA consisted of five phases from upstroke to phase four in control group. APD50 and APD90 of LAPW in control were significantly longer than those of LAA （ P 〈 0. 05, respectively）. With the administration of ouabain （ 1μmol/L）, action potentials of both LAPW and LAA were in a shape of an acute triangle. APD50, APD50, resting potential （RP） and AP amplitude （APA） of both LAPW and LAA were markedly decreased （compared with control, P 〈 0.01 and P 〈0.05, respectively）. Moreover, APD50 and APD50 of LAPW were obviously shorter than those of LAA after ouabain was administered （P 〈 0. 05, respectively）. With voltage clamp protocol of Ica-L, the current densities of LAPW Ica-L were markedly decreased （ compared with that of LAA Ica-L, P 〈 0. 05 ）. With the addition to ouabain （ 1 μmoL/L）, the peak amplitude of LAPW Ica-L and LAA Ica-L increased to （ - 11.13±0. 99 ）pA/pF and （ -8.86 ±0. 51 ）pA/pF （P 〈0. 01, respectively）. In the control group, the I-V curve of LAPW Ic-L was at the bottom of all I-V curves of Ic-L. The I-V curve of Ic-L in LAPW, with the effect of ouabain, went to the top of I-V curves of Ic-L. Conclusions The distribution properties of ion currents have significant difference between LAPW and LAA in rabbit myocytes. Ouabain could accentuate the electrophysiological heterogeneity which might contribute to the triggering and persistence of atrial fibrillation vulnerability.