二十二碳六烯酸增加大鼠冠状动脉平滑肌细胞大电导钙离子激活钾离子流的机制

Mechanism related to docosahexaenoic acid induced large conductance calcium-activated potassium channel currents increase in coronary smooth muscle cells

目的 探讨二十二碳六烯酸（DHA）增加冠状动脉平滑肌细胞（SMC）大电导钙离子激活钾离子流（BK）的机制.方法酶消化法分离正常大鼠冠状动脉SMC.采用不同钾通道阻滞剂,对冠状动脉SMC的钾离子通道进行鉴定.采用全细胞膜片钳实验技术研究DHA及其代谢产物16,17-环氧二十二碳五烯酸（16,17-EDP）对冠状动脉平滑肌细胞BK通道的影响,并观察加入细胞色素P450环氧化酶抑制剂SKF525A孵育SMC后BK通道电流的变化.结果正常冠状动脉平滑肌细胞BK通道电流约占总钾离子流的（64.2±2.7）%（n=20）.DHA可激活BK通道,半效浓度为（0.23±0.03）μmoL/L,但当使用细胞色素P450环氧化酶抑制剂SKF525A预孵育SMC后,DHA对BK通道的激活作用消失,而DHA代谢产物16,17-EDP可产生与DHA相同的BK通道激活作用,半效浓度为（19.7±2.8）nmol/L.结论 DHA通过细胞色素P450环氧化酶代谢途径激活平滑肌细胞BK通道,从而扩张冠状动脉.

Objective To investigate the mechanism of enhanced large conductance calciumactivated potassium channel currents （BK） in coronary smooth muscle cells （SMCs） by docosahexaenoic acid （DHA）. Methods Coronary SMCs were isolated by enzyme digestion. Potassium channels in coronary SMCs were identified by applications of different potassium blockers. Effects of DHA and its metabolite 16,17-epoxydocosapentaenoic acid （16,17-EDP） on BK channels in the absence and presence of cytochrome P450 epoxygenase inhibitor SKF525A were studied by patch clamp in whole-cell configuration. Results BK channels were widely distributed in SMCs, and BK currents in normal SMCs accounted for （64.2±2.7）%of total potassium currents（n =20）. DHA could activate BK channels, and its 50% effective concentration （EC50） was （0.23±0.03）μmol/L, however, the effect of DHA on BK channels was abolished after SMCs were incubated with cytochrome P450 epoxygenase inhibitor SKF525A. 16,17-EDP, a metabolite of DHA, could reproduce the effects of DHA on BK channels, and its EC50 was （19.7± 2.8） nmol/L.Conclusion DHA and metabolites can activate BK channels and dilate coronary arteries through activating cytochrome P450 epoxygenase pathway.