糖尿病对冠状动脉平滑肌细胞大电导钙激活钾通道的影响

Changes of large conductance Ca^2＋ -activated K^ ＋ channels on coronary smooth muscle cells from diabetic rats

目的 探讨糖尿病对冠状动脉平滑肌细胞大电导钙激活钾通道（BK通道）的影响变化,阐明糖尿病冠状动脉损伤的分子机制.方法 采用链脲霉素腹腔内注射建立大鼠糖尿病动物模型,酶消化法分离冠状动脉平滑肌细胞,全细胞膜片钳实验技术和Western blot分别记录和测定正常和糖尿病大鼠冠状动脉平滑肌细胞BK通道电流和亚基的表达;采用荧光测定方法测定正常和糖尿病大鼠冠状动脉平滑肌细胞内钙离子浓度.结果 当刺激电压＞100 mV时,糖尿病冠状动脉平滑肌细胞BK通道电流密度明显低于正常冠状动脉平滑肌细胞BK通道电流密度（P＜0.05）,在刺激电压为150 mV时,电流密度分别为（275±40）pA/pF（n=8）和（70±10）pA/pF（n=6）;与正常组比较,糖尿病组BK通道α亚基蛋白表达差异无统计学意义（P＞0.05）,但β1亚基蛋白表达较低（P＜0.05）;正常组和糖尿病组冠状动脉平滑肌细胞内钙离于浓度分别为（92±7）nmol/L（n=5）和（151±18）nmol/L（n=6）,差异有统计学意义（P＜0.05）.结论 糖尿病冠状动脉平滑肌细胞BK通道β1亚基表达下调、BK通道电流密度下降及细胞内钙离子浓度升高可能是糖尿病冠状动脉功能损伤的重要原因.

Objective To investigate the changes of large conductance Ca2＋ - activated K＋ channel （BK channel ） on coronary smooth muscle cells from diabetic rats. Methods Streptozotocin-induced rat diabetic animal model was used. Coronary smooth muscle cells were isolated by enzyme digestion. BK currents in control and diabetic groups were recorded by patch clamp technique in whole cell configuration,and BK channel protein expression was detected by Western blot Calcium concentration was measured by fluorescence assay. Results Compared with control group, BK current densities in diabetic group were significantly decreased when test potentials 〉 100 mV （P 〈 0.05 ）. BK current densities were （275 ± 40）pA/pF in control group （n =8） and （70 ± 10）pA/pF in diabetic group （n =6） at 150 mV test potentials. α-subunit protein expression was similar between the groups （ P 〉 0. 05 ）, however, β1-subunit protein expression was significantly reduced in diabetic group than in control group （ P 〈 0. 05 ）. Calcium concentrations were significantly increased in diabetic group control group （151 ± 18） nmol/L （n =6） than in control group （92 ±7） nmol/L （n =5, P〈0.05）. Conclusion Observed β1-subunit downregulation,BK current density decrease and cytosolic calcium concentration increase in smooth muscle cells of diabetic coronary arteries may be associated with coronary dysfunction in diabetic rats.