Itakura N, Fisher A B, Thurman R G
J Appl Physiol Respir Environ Exerc Physiol. 1977 Aug;43(2):238-45. doi: 10.1152/jappl.1977.43.2.238.
Oxidative demethylation of p-nitroanisole, a cytochrome P450-linked mixed-function oxidation, was evaluated in isolated perfused rat and rabbit lungs. The product, p-nitrophenol, was monitored continuously in the lung effluent by spectrophotometric measurement. Pulmonary p-nitrophenol production in mumol/h per g dry wt was 6.2+/-0.4 by rabbits and 2.0+/-0.3 by rats (mean+/-SE). Maximal activity of the reaction required pulmonary perfusion rates in excess of 60-80 ml/min per g of dry lung. The half-maximal rate of p-nitrophenol production was observed with p-nitroanisole concentration of 13 micron. Pretreatment of rabbits with chlorpromazine increased p-nitroanisole O-demethylation activity by 63% but phenobarbital pretreatment had no effect. Ventilation with 75% carbon monoxide plus 20% O2 reversibly inhibited the reaction. Specific activity of p-nitroanisole demethylase in the microsomal fraction was 0.5 nmol/min per mg protein in rabbit lungs and 0.1 nmol/min per mg protein in rat lungs. Other rabbit lung subcellular fractions compared with microsomes had significantly lower specific activity. This study demonstrates that p-nitroanisole O-demethylation can be continuously monitored in the intact lung and describes conditions necessary for maximal activity of this pathway.
对硝基苯甲醚的氧化脱甲基作用是一种与细胞色素P450相关的混合功能氧化反应，在离体灌注的大鼠和兔肺中进行了评估。通过分光光度法连续监测肺流出液中的产物对硝基苯酚。每克干重每小时以微摩尔计的肺对硝基苯酚生成量，兔为6.2±0.4，大鼠为2.0±0.3（平均值±标准误）。该反应的最大活性需要肺灌注速率超过每克干肺60 - 80毫升/分钟。当对硝基苯甲醚浓度为13微摩尔时，观察到对硝基苯酚生成的半最大速率。用氯丙嗪预处理兔子可使对硝基苯甲醚O - 脱甲基活性增加63%，但苯巴比妥预处理无作用。用75%一氧化碳加20%氧气通气可使该反应可逆性抑制。兔肺微粒体部分对硝基苯甲醚脱甲基酶的比活性为每毫克蛋白0.5纳摩尔/分钟，大鼠肺为每毫克蛋白0.1纳摩尔/分钟。与微粒体相比，兔肺的其他亚细胞部分比活性显著较低。本研究表明对硝基苯甲醚O - 脱甲基作用可在完整肺中连续监测，并描述了该途径最大活性所需的条件。
