Acclimatization and Adaptation to Chronic Hypoxia, Focusing on Changes in Pulmonary Blood Flow Distribution

本文观察了慢性低氧习服（10%O_2，3周）大鼠和非习服（NA）大鼠安静和亚极量运动时肺血流量（PBF）的区域分布。A组和NA组大鼠均在低氧（10%O_2）和常氧条件下运动。局部PBF分布测定使用非放射性微球注入右心房。正常氧暴露的NA大鼠肺组织PBF呈中心-外周梯度分布，运动对PBF分布无影响。PBF模式没有改变急性缺氧在休息条件下，然而，PBF分布的异质性表现出显着增加在急性缺氧运动。在A大鼠中，相对于NA大鼠，在休息时观察到的中枢至外周梯度减弱;缺氧和常氧条件下均是如此。常氧运动并没有影响A组大鼠PBF的分布，然而，正如NA组大鼠所发生的那样，低氧运动期间PBF分布的异质性显著增加。这些数据表明，PBF在大鼠中的相对均匀的分布改变了缺氧和运动的组合，这表明缺氧性肺血管收缩和血流量升高是必要的，以显着增加PBF分布的异质性。低氧运动时PaO_2显著升高，提示肺气体交换效率较高。这可能是因为PBF分布的变化与低氧运动期间通气分布的平行变化相匹配。

Regional distribution of pulmonary blood flow (PBF) was studied at rest and during submaximal exercise in rats acclimatized to chronic hypoxia (10% O_2 for 3 weeks, A rats) and in nonacclimatized (NA) littermates. Both A and NA rats exercised in hypoxia (10% O_2) or in normoxia. Regional PBF distribution was determined using nonradioactive microspheres injected into the right atrium. The lungs were cut into 28 samples to determine the relative specific PBF of each sample.The NA rats exposed to normoxia showed a central-to-peripheral gradient of PBF distribution which was not modified by exercise. The PBF pattern was not altered by acute hypoxia during resting conditions ; however, the heterogeneity of PBF distribution showed a significant increase during exercise in acute hypoxia. In the A rats, the central-to-peripheral gradient observed at rest was attenuated with respect to that of the NA rats ; this was the case for both hypoxic and normoxic conditions. Normoxic exercise did not influence the distribution of PBF in the A rats ; however, as it happened in the NA rats, PBF distribution showed a significant increase in heterogeneity during hypoxic exercise. These data indicate that the relatively homogeneous distribution of PBF in the rat is altered by the combination of hypoxia and exercise, suggesting that both hypoxic pulmonary vasoconstriction and elevated blood flow are necessary to significantly increase the heterogeneity of PBF distribution. Pao_2 significantly increased during hypoxic exercise, suggesting a higher efficacy of pulmonary gas exchange. This could be because the changes in PBF distribution are matched by parallel changes in the ventilation distribution during hypoxic exercise.