主动脉平滑肌钙激活钾通道的增龄变化

目的研究不同月龄大鼠主动脉平滑肌细胞钙激活钾通道的活性,探讨老化过程中血管平滑肌细胞钙激活钾通道的变化。方法取三组Wistar大鼠(分别为1月龄、6月龄、20月龄各20只)主动脉用酶消化法获得单个平滑肌细胞。以膜片钳技术检测细胞钙激活钾通道的活性,记录不同钳制电压下单通道电流的平均开放时间、平均关闭时间、平均开放概率、电流幅值,并绘制成电流—电压关系曲线。对比各月龄组Wistar大鼠主动脉平滑肌细胞钙激活钾通道活性。结果(1)各月龄组大鼠主动脉平滑肌细胞随着膜电位从+10 mV向+60 mV方向去极化,钙激活钾通道的电流强度逐渐加大,但加大幅度随月龄增加而降低。1月龄、6月龄和20月龄大鼠主动脉平滑肌细胞钙激活钾通道的电导值分别为192±47 ps、177±56 ps和163±35 ps,但差异无统计学意义(P>0.05)。(2)在内面向外式膜片上,20月龄和1月龄大鼠主动脉平滑肌细胞钙激活钾通道平均开放概率分别为0.009±0.001和0.015±0.004,两组比较具有显著性差异(P<0.01)。20月龄和1月龄大鼠主动脉平滑肌细胞钙激活钾通道平均关闭时间分别为2 260±653和2 512±185*,两组比较具有显著性差异(P<0.01)。(3)在同样的对称性高钾浴液中,加入不同浓度钙后,发现钙对各月龄组大鼠主动脉平滑肌细胞钙激活钾通道均有明显的激活作用,表现为平均开放概率逐渐加大,平均关闭时间逐渐缩短。但对各月龄相同钙浓度间比较发现,6月龄组平均开放概率比1月龄加大,而20月龄组平均开放概率和平均开放时间比6月龄和1月龄组均显著降低。结论大鼠主动脉平滑肌细胞钙激活钾通道的活性随着年龄增大而下降。

Research of Changement of Calcium-Activated Potassium Channels in Rat Aortic Smooth Muscle with Aging

Aim To investigate the changes of Ca²⁺-activated K~+(KCa) channels of rats aortic smooth muscle cells with aging.Methods The aortic smooth muscle cells from rats of three groups(1,6,20 months,n=20 respectively) was digested by enzyme and studied the activity of KCa in the rats aortic smooth muscle cells by the Patch-clamp technique.The signal channel open probability(Po),open dwell-time(To),close dwell-time(Tc) and urrent ampitude(AM) were recorded.Results(1)The conductance of the rats aortic smooth muscle cells of 1,6,20 months was 192±47 ps,177±56 ps,163±35 ps respectively.There was no significant difference in each group(p>0.05).But the AM of the rats aortic smooth muscle cells decresed with aging.(2)The Po of KCa in the rats aortic smooth muscle cells was 0.009±0.001,0.015±0.004 respectively,The Tc was 2260±653,2512±185 respectively in 20 month-old rats and in 1 month-old rats under inside-out patch.The activity of KCa had significant difference between two groups(p<0.01).(3)The sensitity of KCa channel to Ca²⁺ in the aortic smooth muscle cells from different month-old rats: After adding Ca²⁺(5×10~(-7),10~(-6),10~(-5) mol/L) to cytoplasm,the Po incresed and the Tc decresed in each group.While comparison of different month-old rats,the Po and the To of 20 month-old rats was less than that of 6 month-old rats and 1 month-old rats.Conclusion The activity of KCa reduced in rats aortic smooth muscle with aging