Kreisman N R, Sick T J, LaManna J C, Rosenthal M
Brain Res. 1981 Aug 10;218(1-2):161-74. doi: 10.1016/0006-8993(81)91298-1.
Simultaneous measurements were made from rat cerebral cortex, in situ, of focal changes in both tissue oxygen tension (ptO2) and the reduction/oxidation ratio of cytochrome c oxidase (cytochrome a,a3) in order to study relationships between oxygen supply and consumption in small regions of tissue. Local ptO2 was measured with polarographic microelectrodes and the redox state of cytochrome a,a3 with a dual wavelength reflectance spectrophotometer. Increased ptO2, produced by respiration of gas mixtures with elevated O2 and/or CO2 content, was accompanied by increased oxidation of cytochrome a,a3. This confirms that cytochrome oxidase is not fully oxidized in focal brain tissue regions in vivo, as it is in mitochondria isolated in vitro. Decreased ptO2 was accompanied by cytochrome a,a3 reduction. The oxidative changes of cytochrome a,a3 with increases in ptO2 were smaller than the reductive changes associated with decreases in ptO2. Curves relating cytochrome a,a3 redox state to ptO2 were qualitatively alike, regardless of the initial ptO2 value from which they were generated. Thus, the reduction level of cytochrome a,a3 varied with ptO2 on a continuum. This consistent relationship demonstrates that changes in mitochondrial redox state provide an index of relative changes in tissue oxygenation in intact neocortex. The results suggest also that local rates of cerebral oxidative metabolism may not always be constant with changes in local ptO2.
为了研究组织小区域内氧气供应与消耗之间的关系，在原位对大鼠大脑皮层同时进行了组织氧张力（ptO2）和细胞色素c氧化酶（细胞色素a，a3）还原/氧化比的局部变化测量。使用极谱微电极测量局部ptO2，并用双波长反射分光光度计测量细胞色素a，a3的氧化还原状态。呼吸含氧量和/或二氧化碳含量升高的混合气体导致ptO2升高，同时细胞色素a，a3的氧化增加。这证实了细胞色素氧化酶在体内局灶性脑组织区域中并未完全氧化，这与体外分离的线粒体情况不同。ptO2降低伴随着细胞色素a，a3的还原。细胞色素a，a3随ptO2升高的氧化变化小于与ptO2降低相关的还原变化。无论生成细胞色素a，a3氧化还原状态与ptO2关系曲线的初始ptO2值如何，这些曲线在定性上都是相似的。因此，细胞色素a，a3的还原水平随ptO2在一个连续体上变化。这种一致的关系表明，线粒体氧化还原状态的变化提供了完整新皮层中组织氧合相对变化的指标。结果还表明，局部脑氧化代谢率可能并不总是随局部ptO2的变化而恒定。
