Research for oxygen sensitive ionic channels of vascular smooth muscle cells

利用全细胞电压钳对血管平滑肌（VSM）细胞的O_2敏感离子通道进行了研究。我们在2000-2001两年内发现了以下结果。为了探讨Na-Ca交换在缺氧诱导的血管收缩中的作用，我们观察了阻力肺动脉（PA）发育过程中Na-Ca交换电流的变化。结论：Na-Ca交换器存在于早熟和成熟的耐药PA中。缺氧使成熟的PA - VSM细胞的Na-Ca向内交换电流减弱。在早抗性PA中，通过Na-Ca交换挤出细胞质Ca的活性增加可能补偿了缺氧诱导的[Ca]i升高。动脉导管收缩（DA）并不经常发生在早产新生儿（NB）。作为DA的O_2传感器，O_2敏感的K_V和K_<ATP>离子通道可能在早产NB中发育不全。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，O_2敏感的K_V和K_<ATP>均发育不全。除了O_2敏感的K_V外，K_<ATP>在da中也可能是重要的O_2传感器。在缺氧条件下，o2敏感的K_V可能关闭，导致PA血管收缩，K_<ATP>可能被激活，防止血管过度收缩。本研究旨在探讨K_<ATP>在抵抗性PA VSM细胞的发育变化。结论：在NB中，KATP存在于小阻力PA中，并随着发展而降低。由于膜电位在-60 ~ 0 mV之间的小PA电流较小，K_<ATP>的作用在生理条件下可能不重要，但在新生儿围生期缺氧条件下可能对血管舒张有重要作用。

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.