Cardiorespiratory Regulation in Endothelin- 1 Gene Knockedout Mice

我们成功培育了内皮素(ET)-1基因敲除小鼠，并将其用于后续实验。1)我们能够在没有任何限制和麻醉的情况下获得小鼠血压和心率的稳定记录，持续时间超过2小时。在计算机的帮助下，获得了大量的数据。2)通过体体积描记术，我们测量了成熟和新生有意识小鼠的通气运动及其对缺氧或高碳酸血症的反射变化。3)我们记录了经脲麻醉的成年小鼠膈神经放电，并测量了其对缺氧或高碳酸血症的反射变化。4)最后，我们测试了血压波动的功率谱分析是否可以用于小鼠自主神经功能的评估方法。因此，完全失去ET-1基因的纯合子在出生后不久就会因颅面组织的异常形成而死亡。另一方面，血浆ET-1浓度约为正常小鼠的一半的杂合子，其血压明显高于对照组。与野生型相比，ET-1缺陷杂合小鼠动脉pO_2显著降低，pCO_2有升高趋势，pH有降低趋势。当这些有意识的小鼠呼吸室内空气时，两组之间的呼吸分钟量和频率没有差异，尽管ET-1^<+/->杂合子对缺氧或高碳酸血症的反射增加明显减弱。由于反射反应受损也可以通过记录膈神经放电得到证实，因此通气功能受损的原因至少部分在于神经系统。此外，在剖宫产和气管切开分娩的纯合子中，通气反射增加严重减弱。因此，ET-1在呼吸的反射控制中起着关键作用。ET-1缺陷小鼠呼吸调节异常可能是导致血压升高的原因。事实上，血压波动的功率谱分析也提示了类似的心肺异常。综上所述，ET-1参与小鼠发育和心肺调节。这是一个重要的新发现，并扩大了ET-1不仅仅是血管收缩剂，而是多种生理作用的参与者的观点。此外，很明显，许多研究整个动物自主神经功能的技术，经过一些修改，也可以用于像老鼠这样的小动物。少

We successfully developed endothelin (ET)-1 gene knckout mice and used them in the following experiment. 1) We were able to obtain stable recordings of the mice's blood pressure and heart rate, without any restriction nor anesthesia, for more than 2 hours. Obtained large quantity of data was handled with an aid of a computer. 2) By body plethysmography, we measured ventilation movement and its reflex change to hypoxia or hypercapnia in mature and new born conscious mice. 3) We recorded phrenic nerve discharges in urethane-anesthetized adult mice and measured their reflex change in response to hypoxia or hypercapnia. 4) Finally, we tested whether power spectral analysis of blood pressure fluctuations could be used in the mice as an evaluation method of autonomic nerve function.As a result, homozygotes that completely lost ET-1 gene died soon after birth by abnormal formation of craniofacial tissues. On the other hand, heterozygotes of which plasma concentration of ET-1 was about half of … More the normal mice showed significantly higher blood pressure than in the controls. In ET-1 deficient heterozygous mice, arterial pO_2 was significantly lower, pCO_2 tended to be higher and pH tended to be lower than in wild-type littermates. When these conscious mice breathed room air, respiratory minute volume and rate were not different between the two groups, although reflex increase to hypoxia or hypercapnia was significantly attenuated in ET-1^<+/-> heterozygotes. Since impaired reflex responses were also evident by recording phrenic nerve discharges, the cause of ventilatory impairment lay, at least in part, in the nervous system. Furthermore, in homozygotes that were delivered by cesarian sections and tracheotomized, reflex increase in ventilation was severely attenuated. Thus ET-1 plays a pivotal role in reflex control of respiration. Abnormality of breathing regulation in ET-1 deficient mice may account for the elevated blood pressure. In fact, similar cardiorespiratory abnormality was suggested by power spectrum analysis of blood pressure fluctuations.In summary, ET-1 participates in development and cardiorespiratory regulation in mice. This is an important and new finding and widens the suggested notion that ET-1 is not a mere vasoconstrictor but a playr of a variety of physiological roles. Moreover, it becomes clear that many of the techniques to study autonomic nervous function in the whole animal can be used in such a small animal as mouse with some modifications. Less