Matsumoto H, Oda T, Hossain M A, Yoshimura N
Department of Anesthesiology and Critical Care Medicine, Kagoshima University School of Medicine, Japan.
Anesth Analg. 1996 Sep;83(3):513-8. doi: 10.1097/00000539-199609000-00012.
We studied cerebral oxygen metabolism during hypoxia to demonstrate whether the redox state of cytochrome aa3 (cyt.aa3), as measured by near infrared spectrophotometry (NIRS), reflects brain energy level. Rats (n = 6) subjected to hypoxia were simultaneously monitored by NIRS and 31P nuclear magnetic resonance spectroscopy (NMRS). Brain function was evaluated using the electroencephalogram (EEG). After a reduction of the fraction of inspired oxygen FIO2 from 0.21 to 0.15, we observed a significant increase in reduced cyt.aa3 (from 16.5% +/- 2.1% to 41.2% +/- 2.8%; P < 0.01), without significant changes in phosphocreatine (PCr) and beta-adenosine triphosphate (beta-ATP) levels. The PCr decreased significantly at a FIO2 of 0.10 (53.8% +/- 6.4% as compared with 97.7% +/- 10.9% at a FIO2 of 0.21; P < 0.05), and reached a minimum at a FIO2 of 0.04. beta-ATP did not change significantly at a FIO2 of 0.10 or 0.08. With a FIO2 of less than 0.08, cyt.aa3 was almost totally reduced. EEG activity slowed at a FIO2 of 0.08 and became isoelectric at 0.04. Significant correlations were found between the levels of cyt.aa3 and PCr (P < 0.001, r = 0.83) as well as between cyt.aa3 and beta-ATP (P < 0.001, r = 0.73) by using the overall values at FIO2 levels from 0 to 1.0. However, no significant correlations were observed among these variables when the FIO2 was less than 0.10. These findings suggest that the increase in reduced cyt.aa3 reflects brain energy depletion; however, the redox state of cyt.aa3 will not indicate brain energy depletion during extreme hypoxia because cyt.aa3 is reduced totally during hypoxia insufficient to deplete intracellular ATP.
我们研究了缺氧期间的脑氧代谢，以证明通过近红外分光光度法（NIRS）测量的细胞色素aa3（cyt.aa3）的氧化还原状态是否反映脑能量水平。对6只遭受缺氧的大鼠同时采用NIRS和31P核磁共振波谱法（NMRS）进行监测。使用脑电图（EEG）评估脑功能。在将吸入氧分数（FIO2）从0.21降至0.15后，我们观察到还原型cyt.aa3显著增加（从16.5%±2.1%增至41.2%±2.8%；P<0.01），而磷酸肌酸（PCr）和β-三磷酸腺苷（β-ATP）水平无显著变化。在FIO2为0.10时PCr显著降低（与FIO2为0.21时的97.7%±10.9%相比为53.8%±6.4%；P<0.05），并在FIO2为0.04时降至最低。在FIO2为0.10或0.08时β-ATP无显著变化。当FIO2小于0.08时，cyt.aa3几乎完全被还原。在FIO2为0.08时EEG活动减慢，在0.04时变为等电位。通过使用FIO2水平从0至1.0的总体值，发现cyt.aa3水平与PCr之间存在显著相关性（P<0.001，r=0.83）以及cyt.aa3与β-ATP之间存在显著相关性（P<0.001，r=0.73）。然而，当FIO2小于0.10时，在这些变量之间未观察到显著相关性。这些发现表明还原型cyt.aa3的增加反映了脑能量消耗；然而，在极端缺氧期间cyt.aa3的氧化还原状态不会表明脑能量消耗，因为在不足以耗尽细胞内ATP的缺氧期间cyt.aa3会完全被还原。
