Cooper C E, Delpy D T, Nemoto E M
Department of Biological Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK.
Biochem J. 1998 Jun 15;332 ( Pt 3)(Pt 3):627-32. doi: 10.1042/bj3320627.
Near-infrared spectroscopy was used to determine the effect of changes in the rate of oxygen delivery to the adult rat brain on the absolute concentrations of oxyhaemoglobin, deoxyhaemoglobin and the redox state of the CuA centre in mitochondrial cytochrome oxidase. The cytochrome oxidase detection algorithm was determined to be robust to large changes in haemoglobin oxygenation and concentration. By assuming complete haemoglobin deoxygenation and CuA reduction following mechanical ventilation on 100% N2O, the absolute concentration of oxyhaemoglobin (35 microM), deoxyhaemoglobin (27 microM) and the redox state of CuA (82% oxidized) were calculated in the normal adult brain. The mean arterial blood pressure was decreased by exsanguination. When the pressure reached 100 mmHg, haemoglobin oxygenation started to fall, but the total haemoglobin concentration and oxidized CuA levels only fell when cerebral blood volume autoregulation mechanisms failed at 50 mmHg. Haemoglobin oxygenation fell linearly with decreases in the rate of oxygen delivery to the brain, but the oxidized CuA concentration did not start to fall until this rate was 50% of normal. The results suggest that the brain maintains more than adequate oxygen delivery to mitochondria and that near-infrared spectroscopy may be a good measure of oxygen insufficiency in vivo.
近红外光谱法用于确定成年大鼠大脑氧气输送速率的变化对氧合血红蛋白、脱氧血红蛋白的绝对浓度以及线粒体细胞色素氧化酶中铜A中心氧化还原状态的影响。已确定细胞色素氧化酶检测算法对血红蛋白氧合作用和浓度的大幅变化具有稳健性。通过假设在100%一氧化二氮机械通气后血红蛋白完全脱氧和铜A还原，计算出正常成年大脑中氧合血红蛋白的绝对浓度（35微摩尔）、脱氧血红蛋白（27微摩尔）和铜A的氧化还原状态（82%氧化）。通过放血降低平均动脉血压。当血压降至100 mmHg时，血红蛋白氧合作用开始下降，但只有当脑血容量自动调节机制在50 mmHg时失效，总血红蛋白浓度和氧化型铜A水平才开始下降。血红蛋白氧合作用随大脑氧气输送速率的降低呈线性下降，但氧化型铜A浓度直到该速率降至正常的50%时才开始下降。结果表明，大脑向线粒体输送的氧气量充足，近红外光谱法可能是体内氧不足的良好测量方法。
