多巴胺舒张猪冠状动脉及激活冠状动脉平滑肌细胞钾通道

采用血管环实验和膜片钳细胞贴附式技术分别在器官和细胞分子水平观察多巴胺舒张猪冠状动脉作用及对平滑肌细胞大电导型钙激活钾通道(BK_Ca)的影响. 结果表明多巴胺引起前列腺素F_2α(PGF_2α)预收缩动脉环浓度依赖性舒张反应, 而不引起高K⁺预收缩动脉环舒张反应. 表明多巴胺引起的冠状动脉血管舒张反应依赖于K⁺生理浓度梯度的存在, 结果提示钾通道参与了多巴胺的血管舒张反应. 向细胞浴液内灌流多巴胺增强冠状动脉血管平滑肌细胞膜BK_Ca通道活性. 用DA₁受体阻断剂SCH23390预处理细胞, 完全阻断多巴胺的这一作用, 而用β受体阻断剂普萘洛尔无影响. 提示多巴胺通过DA₁受体激活BK_Ca通道引起PGF_2α预收缩动脉环舒张反应.

Dopamine relaxes porcine coronary arteries and stimulates potassium channel activity in porcine coronary arterial smooth muscle cells

The relaxing effect of dopamine on isolated coronary vessels and the activating effect of dopamine on large-conductance, calcium-activated potassium channels（BK_Ca） in the membrane of coronary myocytes were investigated with isometric tension recording method and patch-clamp technique. Tension studies demonstrated that dopamine relaxed prostaglandin F_2α nduced contraction of porcine coronary arteries in a concentration-dependent manner, but it failed to relax high［K⁺］ precontracted arteries. In cell attached patch experiments, dopamine caused a significant increase in the mean opening probability of the BK_Ca channels. The effect of dopamine was not blocked by propranolol but was completely prevented by SCH23390, a selective DA₁ antagonist. These results demonstrate that dopamine relaxes prostaglandin F_2α induced contraction of porcine coronary arteries via activation of DA₁ receptors which causes stimulation of BK_Ca channel activity.