二十二碳六烯酸对大鼠冠状动脉平滑肌细胞大电导钙激活性钾通道的影响

目的探讨二十二碳六烯酸(DHA)对大鼠冠状动脉平滑肌细胞(CASMCs)上大电导钙激活性钾通道(BKCa)的影响。方法采用酶消化法获得大鼠CASMCs,用膜片钳技术分别记录0,10,20,40,60和80μmol/LDHA对大鼠CASMCs上BKCa通道动力学的影响。结果在不同浓度DHA作用下,IBKCa和BKCa尾电流均呈浓度依赖性增加。IBKCa和BKCa尾电流I-V曲线均上移,对IBKCa稳态激活曲线无影响。在指令电压+150 mV,不同浓度DHA作用下,IBKCa电流密度分别为68.24±22.75,72.40±24.49,120.44±37.96,237.48±53.22,323.60±74.83和370.61±88.16pA/pF(P<0.05,n=20)。DHA对IBKCa激活的药物半效浓度为36.22±2.17μmol/L。在测试电压+90 mV,不同浓度DHA作用下,BKCa尾电流密度分别为91.02±13.52,100.23±17.34,224.02±38.76,369.19±65.39,511.39±82.77和700.14±96.64 pA/pF(P<0.05,n=20)。结论 DHA对全细胞BKCa有激活作用,对稳态激活曲线无影响。DHA对BKCa通道的激活作用可能是其舒张血管机制之一。

Effects of docosahexaenoic acid on large-conductance Ca2+-activated K+ channels in rat coronary artery smooth muscle cells

Objective To investigate the effects of docosahexaenoic acid （DHA） on large-conductance Ca^2＋ -activated K^＋ （BKca） channels in rat coronary artery smooth muscle cells （CASMCs）. Methods Rat CASMCs were isolated by enzyme digestion method. BKCa currents in individual CASMC were recorded by patch-clamp technique in whole-cell configuration at room temperature. Effects of DHA on BKca channels were observed when it was applied at 0, 10, 20, 40, 60 and 80 μmol/L respectively. Results IBKCa were gradually increased, Ⅰ-Ⅴ curves were upward shifted, and BKca tail currents were gradually increased, BKCa tail currents Ⅰ-Ⅴ curves were upward shifted with augmentation of DHA, and stably activated curves were of no remarkable significance at different concentration of DHA. IBKCa current densities were 68.24 ± 22.75, 72. 40 ± 24.49, 120.44 ± 37.96, 237.48 ± 53.22, 323.60 ± 74.83 and 370.61 ± 88.16pA/pF （P 〉 0. 05, n = 20） with 0, 10, 20, 40, 60 and 80 μmol/L of DHA and the half-effective concentration of DHA was 36.22 ± 2.17 μmol/L. BKCa tail current densities were 91.02 ± 13.52, 100.23 ± 17.34,224.02 ± 38.76, 369.19 ± 65.39, 511.39 ± 82.77 and 700.14± 96.64A/ pF （P 〈0. 05, n = 20） respectively at above DHA concentrations. Conclusion DHA can activate BKCa channels in CASMCs of rat, which indicates that the vasorelaxation effects of DHA on vascular smooth muscle ceils are mainly due to its activating effect on BKCa channels.