Ritter C L, Malejka-Giganti D
Biochem Pharmacol. 1982 Jan 15;31(2):239-47. doi: 10.1016/0006-2952(82)90217-9.
Mammary gland and liver microsomes of lactating rats were examined for the components of mixed function oxidase and related enzyme activities. Cytochrome b5, NADH- and NADPH- dependent cytochrome c reductase activities were 15-, 6- and 10-fold lower, respectively, in the mammary gland than in the liver microsomes. The determination of cytochrome P-450 (P-448) in the mammary gland microsomes required elimination of the spectral interferences by hemoglobin and cytochrome aa3. The presence of the latter in this fraction was also shown by cytochrome c oxidase activity. Cytochrome aa3 was reduced by anaerobic incubation of mammary gland microsomes, in the presence of antimycin A, with sodium succinate, phenazine ethosulfate, and sodium ascorbate for 30 min at room temperature. Spectral resolution of the dithionite-reduced cytochrome P-450 (P-488) carbon monoxide complex occurred 30 min after gassing. The basal level of cytochrome P-450 was about 500-fold greater in the liver than in the mammary gland microsomes. Pretreatment of lactating rats with the inducers of hepatic cytochrome P-448, 3-methylcholanthrene and beta-naphthoflavone, increased the cytochrome content 3- to 10-fold, in the mammary gland and liver microsomes, respectively. The induction of cytochrome P-448 in microsomes of both tissues was also shown by type I binding spectra obtained with N-2-fluorenylacetamide. Using hydroxylation of benzo[a]pyrene and N-2-fluorenylacetamide as a measure of mixed function oxidase activity, we found that the basal activities, which were 4- to 8-fold greater in the liver microsomes, were increased in both tissues after treatment of rats with the inducers. The induced activities were inhibited by 0.1 micrometers alpha-napthoflavone in vitro, indicating a dependence on cytochrome P-448. The data suggest that the mammary gland, an extrahepatic target for carcinogens, is capable of their metabolism.
对泌乳大鼠的乳腺和肝脏微粒体进行了混合功能氧化酶成分及相关酶活性的检测。乳腺中的细胞色素b5、依赖NADH和NADPH的细胞色素c还原酶活性分别比肝脏微粒体低15倍、6倍和10倍。测定乳腺微粒体中的细胞色素P - 450（P - 448）需要消除血红蛋白和细胞色素aa3的光谱干扰。细胞色素c氧化酶活性也表明该组分中存在细胞色素aa3。在抗霉素A存在下，将乳腺微粒体与琥珀酸钠、吩嗪硫酸乙酯和抗坏血酸钠在室温下厌氧孵育30分钟，细胞色素aa3被还原。通氮气30分钟后，连二亚硫酸盐还原的细胞色素P - 450（P - 488）一氧化碳复合物出现光谱分辨率。肝脏中细胞色素P - 450的基础水平比乳腺微粒体高约500倍。用肝细胞色素P - 448诱导剂3 - 甲基胆蒽和β - 萘黄酮对泌乳大鼠进行预处理，分别使乳腺和肝脏微粒体中的细胞色素含量增加3至10倍。用N - 2 - 芴基乙酰胺获得的I型结合光谱也表明了两种组织微粒体中细胞色素P - 448的诱导。以苯并[a]芘和N - 2 - 芴基乙酰胺的羟化作用作为混合功能氧化酶活性的指标，我们发现肝脏微粒体中基础活性高4至8倍，用诱导剂处理大鼠后，两种组织中的基础活性均增加。体外0.1微米α - 萘黄酮可抑制诱导活性，表明其依赖于细胞色素P - 448。数据表明，作为致癌物肝外靶标的乳腺能够对其进行代谢。
