Research for oxygen sensitive ionic channels of vascular smooth muscle cells

我们用全细胞电压钳技术研究了血管平滑肌(VSM)细胞氧敏感离子通道。我们在两年(2000-2001)的时间里取得了以下成果。为探讨Na-Ca交换在低氧血管收缩中的作用，我们观察了阻力肺动脉(PA)Na-Ca交换电流的发育性变化。结论：早产儿耐药PA和成熟耐药PA均存在钠钙交换。低氧可减弱成熟抗性PA VSM细胞的Na-Ca交换内向电流。在早熟抗性PA中，通过Na-Ca交换排出胞质钙的活性增加可能起到补偿缺氧引起的[Ca]i升高的作用。动脉导管收缩(DA)在早产儿中并不常见。作为DA的氧感受器，氧敏感的Kv和K&lt；ATP&gt；这些离子通道可能在早产儿NB中不发达。本研究的目的是研究这些离子通道在DA VSM细胞中的发育。结论：在DA中，早产儿对O2敏感的Kv和K&lt；ATP&Gt；均发育不良。除了对O_2敏感的K_V外，K_lt；ATP&gt；可能也是DAO_2的重要传感器。在低氧条件下，氧敏感的K_V可能被关闭，导致PA血管收缩，K_lt；ATP&gt；可能被激活，防止过度的血管收缩。本研究旨在探讨耐药PA VSM细胞K&lt；ATP&Gt；的发育变化。结论：在NB中，KATP存在于小阻力PA中，且随发育而减少。由于膜电位在-60-0 mV之间的小PA的电流很小，在生理条件下K&lt；ATP&gt；的作用可能不重要，但在围产期低氧条件下对NB的血管扩张可能是重要的。

We had explored the O_2 sensitive ion channels of vascular smooth muscle (VSM) cells using whole-cell voltage clamp. We found the following results in two years (2000-2001).1. To investigate the role of Na-Ca exchange in the hypoxia induced vasoconstriction, we evaluated the developmental changes of Na-Ca exchange current of the resistance pulmonary artery (PA). Conclusions : The Na-Ca exchanger is present in both the premature and mature resistance PA. Hypoxia attenuates the Na-Ca exchange inward current in the mature resistance PA VSM cells. In the premature resistance PA, the increased activity to extrude cytoplasmic Ca via Na-Ca exchange may function to compensate for the hypoxia induced [Ca]i rise.2. The contraction of ductus arteriosus (DA) does not often occur in premature new born (NB). As an O_2 sensor of DA, O_2 sensitive K_V and K_<ATP> have been implicated and these ion channels may be underdeveloped in premature NB. The purpose of the present study was to investigate development of these ion channels in the DA VSM cells. Conclusions : In the DA, both O_2 sensitive K_V and K_<ATP> are underdeveloped in the premature fetus. In addition to O_2 sensitive K_V, K_<ATP> may also be important as an O_2 sensor in the DA.3. Under hypoxic conditions, O_2 sensitive K_V may be closed, resulting in PA vasoconstriction and K_<ATP> may be activated, preventing excessive vasoconstriction. The purpose of the present study was to investigate developmental changes of K_<ATP> in the resistance PA VSM cells. Conclusions : In NB, KATP is present in the small resistance PA and it decreases with development. Since the currents in the small PA with membrane potential between -60 to 0 mV are small, the role of K_<ATP> may not be important under physiological conditions, but may be important for vasodilation during the perinatal hypoxic conditions in NB.