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

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

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(BKCa)的影响 .结果表明多巴胺引起前列腺素 F2α(PGF2α)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 BKCa通道活性 .用 DA1受体阻断剂 SCH2 3390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 BKCa通道引起

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 induced 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 DA 1 antagonist. These results demonstrate that dopamine relaxes prostaglandin F 2α induced contraction of porcine coronary arteries via activation of DA 1 receptors which causes stimulation of BK Ca channel activity.