Regulation of coronary circulation or pulmonary circulation in the setting of simulated space environments.

为了模拟太空环境，这些动物被倾斜了10度。研究了长期佩戴仪器的犬对冠状动脉血流量的连续测量。在模拟空间环境下，通过20秒闭塞造成的反应性充血评估冠状动脉血流储备没有明显变化。虽然在模拟空间环境下左心室容积几乎没有增加，但阻断导致左心室容积对头向下倾斜的反应增强。这种增强引起冠状动脉血流量的显著增加。这可能是由于在模拟太空环境中心脏的需氧量增加所致。乙酰胆碱引起全身性低血压。这种反应被1-硝基精氨酸甲酯（1-NAME）部分抑制，被mucarinin -1受体阻断剂（Pirenzepine）完全抑制。另一方面，冠状动脉对乙酰胆碱的抵抗反应被1-NAME几乎不受抑制，而被吡renzepin强烈抑制。为了阐明高重力条件对肺循环的影响，建立了EDRF的测定方法，并研究了低肺泡氧对肺血流重力依赖性分布的影响。肺泡低氧使血流从下肺野重新分布到上肺野。

To simulate the space environment, the animals were tilted down by 10degrees.The chronically instrumented dog enabled us to measure coronary blood flow continuously were studied.In the setting of simulated space environment, there was no discernible change in coronary flow reserve assessed by reactive hyperemia created with 20-second occlusion.Although there was little increase in left ventricular volume in the setting of the simulated space environment, the blockade resulted in the augmented response of left ventricular volume to the head-down tilt.This augmentation caused the marked increase in coronary blood flow.This was probably due to increase in oxygen demand of the heart in the setting of simulated space environment.Acetylcholine induced systemic hypotension.This response was partially inhibited by 1-Nitro Arginine Methyl Ester (1-NAME), and was completely inhibited by mucarinic-1 receptor blockade (Pirenzepine).On the other hand, the response of coronary arterial resistance to acetylcholine was hardly inhibited by 1-NAME and strongly inhibited by Pirenzepine.To clarify the effect of high-gravity condition on pulmonary circulation, the determination of EDRF was established and the effects of low alveolar oxygen on the gravity dependent distribution of pulmonary blood flow were studied.Low alveolar oxygen redistributed the blood flow from lower lung field to upper lung field.