Hempel F G, Jöbsis F F, LaManna J L, Rosenthal M R, Saltzman H A
J Appl Physiol Respir Environ Exerc Physiol. 1977 Nov;43(5):873-9. doi: 10.1152/jappl.1977.43.5.873.
The reduction-oxidation level of cytochrome aa3 in the intact cerebral cortex of cerveau isolé or pentobarbital-anesthetized cats was monitored by means of dual-beam reflectance spectrophotometry. Respiratory gases containing varying fractions of carbon dioxide and oxygen were administered at increased pressures, allowing titration of the cytochrome redox state from maximum reduction during nitrogen ventilation to the completely oxidized state. We show that the fully oxidized state could be reached with about 5% CO2-95% O2 inspired at 4 ATA. Maximum oxidation was achieved only through the relaxation of oxygen-induced vasoconstriction of the cerebral vessels, as our data indicated that large blood volume responses accompanied the increases in inspired carbon dioxide. With out technique, we have established that under resting air-breathing conditions cytochrome aa3 is about 85% reduced in the cat cerebral cortex, and that the absorption peak for cytochrome aa3 in situ is located near 602 nm. A free energy change of an additional 8 kcal is calculated to occur with donation of an electron pair from 85% reduced cytochrome aa3 to oxygen as compared to a 1% reduction level.
采用双光束反射分光光度法监测孤立脑或戊巴比妥麻醉猫完整大脑皮层中细胞色素aa3的氧化还原水平。在升高的压力下给予含有不同比例二氧化碳和氧气的呼吸气体，从而将细胞色素的氧化还原状态从氮气通气时的最大还原状态滴定至完全氧化状态。我们发现，在4个绝对大气压下吸入约5%二氧化碳-95%氧气时可达到完全氧化状态。最大氧化仅通过解除氧气诱导的脑血管收缩来实现，因为我们的数据表明，吸入二氧化碳增加时伴有大量血容量反应。通过我们的技术，我们确定在静息呼吸空气条件下，猫大脑皮层中的细胞色素aa3约85%处于还原状态，并且原位细胞色素aa3的吸收峰位于602nm附近。与1%的还原水平相比，计算得出从85%还原的细胞色素aa3向氧气提供一对电子时会发生额外8千卡的自由能变化。
