兔脑微血管与大动脉内皮细胞膜离子通道的比较

Comparison of membrane ion channels of brain microvascular endothelial cells and large aorta in rabbits

目的 :观察培养脑微血管内皮细胞电生理特点 .方法 :培养脑不同部位微血管内皮细胞 ,采用全细胞膜片钳技术 ,在高钾细胞内液和高钠细胞外液条件下观察细胞静息膜电位和电压依赖性电流特点 .结果 :兔脑干、小脑和大脑皮质的微血管内皮细胞静息膜电位分别为 (15± 12 ) ,(2 0± 8)和(31± 16 )mV ,其中脑干和大脑皮层的微血管内皮细胞静息膜电位间有显著性差异 .在本实验条件下 ,乙酰胆碱 (1～ 10 0μmol·L-1)对脑微血管内皮细胞膜电位没有明显影响 ,但可引起兔主动脉和肺动脉内皮细胞膜电位去极化 ,且被阿托品 (6μmol·L-1)抑制 .超极化步脉冲条件下可以记录到一内向性整流性电流 ,去极化条件下则记录到一具有随时间激活的外向性电流 ,以上两种电流均对钾通道阻断剂TEA敏感 ;部分细胞中还可以记录到一种快速激活和快速失活且对钳制电压敏感的电流 .兔脑微血管内皮细胞电流特点与牛主动脉内皮细胞(以内向整流性电流为主 )和兔肺动脉平滑肌细胞 (以外向整流性电流为主 )的电生理特点明显不同 .结论 :兔脑不同部位微血管内皮细胞静息膜电位不同 ;可以记录到 3种类型的钾通道电流 。

AIM: To investigate the electrophysiological characteristics of cultured brain microvascular endothelial cells (BMECs) in rabbits. METHODS: Microvascular endothelial cells from different part of the brain in rabbits were isolated and cultured. The aortic and pulmonary artery endothelial cells and smooth muscle cells isolated from rabbits or bovine were cultured by routine methods. The rest membrane potential and voltage dependent currents were recorded by whole cell patch clamp technique with normal external Na + bath and K + pipette solution. RESULTS: The membrane potential of microvascular endothelial cells from brain stem, cerebellum and cerebral were (15±12), (20±8) and (31±16)mV, respectively. Acetylcholine (Ach, 1-100 μmol·L -1 ) had no significant effects on the membrane potential(MP) of BMECs but it evoked hyperpolarization in aortic and pulmonary artery endothelial cells of bovine and rabbits. The action of Ach could be blocked by atropine (6 μmol·L -1 ). Hyperpolarization pulse elicited an inwardly rectifying current in rabbit BMECs. Outward current was recorded in most cells when depolarization pulse was applied and it had the time dependent activation characteristics. The two currents were all sensitive to TEA, which is one of K + channel blockers. Furthermore a transient outward current was recorded in some cells. Its activation and inactivation was fast and was sensitive to the holding potentials. The ratio of inward and outward currents elicited by hyperpolarization and depolarization pluses of BMECs was very different from that of arotic artery ECs of bovine and of smooth muscle cells of rabbits. CONCLUSION: There is a difference between the rest membrane potential of cultured BMECs and different part of brain in rabbits. The properties of the three K + channels recorded in BMECs in rabbits were different from those of large artery ECs and smooth muscle cells.