Manohar M, Parks C M, Busch M, Bisgard G E
Respir Physiol. 1984 Oct;58(1):111-22. doi: 10.1016/0034-5687(84)90049-5.
Regional distribution of brain blood flow (15 micron diameter radionuclide labelled microspheres injected into the left atrium) was studied in 6 unanesthetized calves during the 7th-8th weeks of exposure to a simulated altitude of 3500 m (PB = 500 mm Hg). Measurements were made during chronic hypoxemia (PaO2 = 48 +/- 1 mm Hg) and acute normoxemia (PaO2 = 91 +/- 1 mm Hg). Five calves, born and raised at sea level, were also studied in a similar manner during normoxemia (PaO2 = 86 +/- 2 mm Hg) and at 12 and 22 min of acute hypoxemia (PaO2 = 49 +/- 1 mm Hg) to serve as controls. Acute hypoxemia in sea level calves resulted in a marked uniform increase in blood flow to all regions of the brain and the brain O2 delivery remained similar to its normoxemic value. By comparison, however, blood flow in all regions of the brain in calves sojourning at 3500 m remained unchanged between hypoxemia and normoxemia. In these calves brain O2 delivery decreased during hypoxemia. These experiments demonstrated that blood flow in the bovine brain-stem and cerebellum behaved in the same manner as in the cerebrum during exposure to acute as well as chronic hypoxia. It is suggested that there are likely to be differences in adaptation of bovine cerebral circulation to acute vs chronic hypoxia.
在6头未麻醉的小牛处于模拟海拔3500米（PB = 500毫米汞柱）环境下的第7 - 8周时，研究了脑血流的区域分布（将直径15微米的放射性核素标记微球注入左心房）。在慢性低氧血症（PaO2 = 48 ± 1毫米汞柱）和急性正常氧血症（PaO2 = 91 ± 1毫米汞柱）期间进行测量。还以类似方式研究了5头在海平面出生并长大的小牛，在正常氧血症（PaO2 = 86 ± 2毫米汞柱）以及急性低氧血症12分钟和22分钟时（PaO2 = 49 ± 1毫米汞柱）作为对照。海平面小牛的急性低氧血症导致脑所有区域的血流显著均匀增加，且脑氧输送保持与其正常氧血症值相似。然而，相比之下，在3500米停留的小牛脑所有区域的血流在低氧血症和正常氧血症之间保持不变。在这些小牛中，低氧血症期间脑氧输送减少。这些实验表明，在暴露于急性和慢性缺氧期间，牛脑干和小脑的血流与大脑的血流表现方式相同。提示牛脑循环对急性与慢性缺氧的适应可能存在差异。
