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电流的影响

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电流(BK_(Ca))的影响。方法采用酶消化法获得大鼠CASMCs,并用单通道内膜向外(inside-out)模式及全细胞膜片钳技术记录,分别加入10、20、30、40、50、60、70和80μmol/L DHA后,大鼠CASMCs的BK_(Ca)变化。结果 (1)单通道inside-out模式下,测试电位-60 mV及DHA浓度>10μmol/L时,BK_(Ca)的开放概率(Po)增大,且呈浓度依赖性,Po从[(0.072±0.003)0μmol/L DHA,n=6]增至[(0.601±0.030)80μmol/L DHA,n=10,P<0.05],半效激活浓度为(36.110±0.080)μmol/L;当DHA浓度<10μmol/L时,Po增加不明显(P>0.05);(2)全细胞模式下,随着DHA浓度增加,BK_(Ca)电流密度逐渐增大,且呈浓度依赖性。测试电位+80 mV,BK_(Ca)电流密度从[(48.9±2.5)pA/pF 0μmol/L,n=6]增至[(226.3±11.3)pA/pF 60μmol/L,n=8,P<0.05]。结论随着DHA浓度的增加,BK_(Ca)Po及电流密度逐渐增大,DHA对BK_(Ca)的影响可能是舒张血管的机制之一。

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

Objective To investigate the effects of DHA on large conductance Ca~(2+)-activated K~+ (BK_(Ca))channel in rat coronary artery smooth muscle cells(SMCs). Methods Rat coronary artery SMCs were isolated by enzyme digestion method. BK_(Ca) currents in individual SMC were measured using patch-clamp technique in an inside-out and whole-cell configuration at room temperature. Effects on BK_(Ca) channel was observed when DHA was added to the perfusate and the final concentrations were 10 μmol/L, 20 μmol/L, 30 μmol/L, 40 μmol/L, 50 μmol/L, 60 μmol/L, 70 μmol/L and 80μmol/L respectively. Results DHA increased BK_(Ca) open probability(Po) in a dose-dependent manner under single channel condition in an inside-out configuration. The open probability of BK_(Ca) channels at testing potential -60 mV increased from [(0.072±0.003) 0 μmol/L] to [(0.601±0.030) 80 μmol/L, P<0.05]. The IC_(50) value was(36.110±0.080) μmol/L. When DHA concentration was <10μmol/L,there was no significant increase in Po (P>0.05). The current density of BK_(Ca) was significantly increased with increasing DHA concentration under whole cell voltageclamp condition. The density of BK_(Ca) at testing potential+80 mV increased from (48.9±2.5) pA/pF 0 μmol/L,to a maximum of(226.3±11.3)pA/pF 60 μmol/L (P<0.05). Conclusions Open probability and current density of BK_(Ca) channel in rat coronary artery SMCs were significantly increased by DHA at different concentrations. These results suggest that DHA can activate BK_(Ca) channels in a dose-dependent manner,which may contribute to the vasorelaxation effects.