二十二碳六烯酸及其代谢产物对正常大鼠冠状动脉平滑肌细胞大电导钙激活钾通道的激活作用

目的研究二十二碳六烯酸（DHA）及其代谢产物16，17-环氧二十二碳五烯酸（16，17-EpDPE）对正常大鼠冠状动脉平渭肌细胞大电导钙激活钾通道（BK）单通道的激活作用，探讨DHA扩张冠状动脉、保护心血管的机制。方法酶消化法分离正常大鼠冠状动脉平滑肌细胞，采用膜内向外型单通道膜片钳实验技术记录0，0．01，0．1，0．3，1，3，5，7．5和10mmol／L浓度下DHA及其代谢产物16，17-EpDPE灌流后BK单通道开放概率。结果在电极外液钙离子浓度为1mmol／L和刺激电位60mV条件下，DHA浓度为0，0．01，0．1，0．3和1mmol／L时，BK通道开放概率分别为0．0914±0．0098，0．0907±0．0102，0．0945±0．0091，0．0986±0．0112和0．1104±0．0145（P〉0．05，n=5）；DHA浓度为3，5，7．5和10mmol／L时，BK单通道开放概率分别为0．6712±0．0456，0．7511±0．0798，0．8424±0．1373和0．8669±0．0967（P〈0．05，n=5），呈浓度依赖性增高。16，17-EpDPE浓度为0，10，50和100nmol／L时，BK单通道开放概率分别为0．1025±0．0114，0．1006±0．0091，0．1128±0．0132和0．1081±0．0143（P〉0．05，n=5）。结论低浓度DHA不能激活BK单通道，高浓度DHA可能通过与BK通道结合并直接激活BK单通道，这可能是DHA扩张冠状动脉的机制之一。

Activation effects of docosahexaenoic acid and its metabolite on BK single channel in coronary smooth muscle cells.

Objective To investigate the activation effects of docosahexaenoic acid（DHA） and its metabolite 16,17-ep- oxydocosapentaenoic acid（ 16, 17-EpDPE）on large conductance Ca2＋-aetivated K＋ channel （BK channel） in coronary smooth muscle cells of rats and to elucidate the mechanisms of DHA-mediated vasodilation and eardio-proteet effects. Methods Coronary smooth muscle cells were isolated by enzyme digestion. Effects of DHA and its metabolite 16, 17-Ep- DPE on BK channels were studied by patch clamp in inside-out single channel configuration. Results In the presence of 0, 0.01, 0.1. 0.3 and 1 mmol/L DHA, the open probabilities of BK channels at 1 mmol/L calcium in external solution and test potentials at 60 mV were 0. 091 4±0.009 8,0. 090 7±0. 010 2,0.094 5±0. 009 1,0. 098 6±0.011 2, and 0.110 4 ±0.014 5 respectively （P〉0.05, n = 5）. On the setting of 3,5,7.5 and 10 mmol/L DHA, the open probabilities of BK channels at 1 mmol/L calcium in external solution and test potentials at 60 mV were 0. 671 2±0. 045 6,0.751 1 ±0.079 8, 0. 842 4±0. 137 3 and 0. 866 9±0. 096 7 respectively （P〈0.05, n = 5 ）. In the presence of 0,10, 50 and 100nmol/L 16,17-EpDPE, the open probabilities of BK channels at 1 mmol/L calcium in external solution and test potentials at 60 mV were 0. 102 5±0.011 4, 0. 100 6±0.009 1,0. 112 8±0. 013 2 and 0. 108 1±0. 014 3 respectively （P〉0.05, n= 5）. Conclusion Low concentration of DHA can＇t activate BK single channels while high concentration of DHA can directly activate BK channels by binding to the channel protein, which may be one of the mechanisms that DHA dilates coronary arteries.