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目的 研究BTHP对豚鼠乳头状肌动作电位及单个心室肌细胞延迟整流钾电流影响的频率依赖性。方法 用标准微电极方法在不同基础周长 (BCL)时测定动作电位 ;采用全细胞膜片钳技术测定延迟整流钾电流 (IK:IKr、IKs)。结果 10 0 μmol·L-1BTHP在BCL为 :2 0 0 0、2 5 0ms时 ,使APD2 0 分别延长 11 35 %和 2 5 5 5 % ;使APD90 分别延长15 97%和 32 5 6 %。 30 μmol·L-1BTHP在刺激频率为 :0 2 5和 2 0Hz时分别使Ikr,tial从 (0 94± 0 .44 ) pA·pF-1和(0 92± 0 31) pA·pF-1降至 (0 6 0± 0 32 ) pA·pF-1和 (0 43± 0 18)pA·pF-1。在刺激频率为 :0 1和 2 0Hz时分别使Iks,tial从 (4 2 2± 0 5 6 ) pA·pF-1和 (5 14± 0 2 8)降至 (2 5 8±0 41)pA·pF-1和 (2 6 2± 0 37)pA·pF-1。结论 BTHP可频率依赖性地阻滞IKr、IKs,其延长动作电位也呈频率依赖性
Objective To study the frequency dependence of the effect of BTHP on the action potentials of the papillary muscles and the delayed rectifier potassium currents of single ventricular myocytes in guinea pigs. Methods The action potentials were measured at different basal circumference (BCL) by standard microelectrode method. The delayed rectifier potassium currents (IK: IKr, IKs) were measured by whole cell patch clamp technique. Results APD20 was prolonged by 11.35% and 25.5% respectively when the BCL was 2.000 and 25.0 ms, while the APD90 was prolonged by 15.97% and 32.56% respectively. 30 μmol·L-1BTHP increased Ikr, tial from (0 94 ± 0.44) pA · pF-1 and (0 92 ± 0 31) pA · pF-1 at 0 2 5 and 20 Hz, respectively Down to (0 6 0 ± 0 32) pA · pF-1 and (0 43 ± 0 18) pA · pF-1. Iks, tial were reduced from (4222 ± 056) pA · pF-1 and (5414 ± 028) to (2558 ± 041) at stimulation frequencies of 0 1 and 20 Hz respectively. pA · pF-1 and (2 6 2 ± 0 37) pA · pF-1. Conclusion BTHP can block IKr and IKs in a frequency-dependent manner, and its prolonged action potentials are also frequency-dependent