2,4,5—三氟苯胺体外代谢生成一氧化碳的途径与三卤苯胺的构…

实验证明，２，４，５－三氟苯胺（ＴＦＡ）与大鼠肝微粒体、ＮＡＤＰＨ和分子氧共存时可经历脱氟、对位羟化和氧化释放一氧化碳（ＣＯ）等代谢过程。与对照组（Ｃｏｎｔｒｏｌ）微粒体相比，苯巴比妥（ＰＢ）或地塞米松（ＤＥＸ）诱导的微粒体，使２，４，５－ＴＦＡ代谢降解为ＣＯ的速度分别提高３－８倍，脱氟速度提高１－４倍，对位羟化速度提高１．９－１．５倍，底物消失速度提高２－２．５倍，而２，４，６－ＴＦＡ，２，４，     

P450ⅢA在2,4,5—三氟苯胺代谢生成一氧化碳中起主导…

２，４，５－三氟苯胺（２，４，５－ＴＦＡ）与空气氧，ＮＡＤＰＨ及地塞米松（ＤＥＸ）预处理的大鼠肝微粒体共温育，可生成大量的一氧化碳（ＣＯ）。但是，未处理或β－萘黄酮预处理的大鼠肝微粒体却无上述能力。与ＤＥＸ相比，苯巴比妥（ＰＢ）诱导的鼠肝微粒体使２，４，５－ＴＦＡ生成ＣＯ的能力仅为前者的１／４。Ｐ４５０ⅢＡ是ＤＥＸ所诱导的最主要的Ｐ４５０亚族，亦能为ＰＢ所诱导，因而在Ｐ４５０ⅢＡ对２，４，５－ＴＦ     

P450ⅢA在2，4，5－三氟苯胺代谢生—氧化碳中起主导作用

２，４，５－三氟苯胺（２，４，５－ＴＦＡ）与空气氧，ＮＡＤＰＨ及地塞米松（ＤＥＸ）预处理的大鼠肝微粒体共温育，可生成大量的一氧化碳（ＣＯ）．但是，未处理或β－萘黄酮预处理的大鼠肝微粒体却无上述能力。与ＤＥＸ相比，苯巴比妥（ＰＢ）诱导的鼠肝微粒体使２，４，５－ＴＦＡ生成ＣＯ的能力仅为前者的１／４．Ｐ４５０ⅢＡ是ＤＥＸ所诱导的最主要的Ｐ４５０亚族，亦能为ＰＢ所诱导，因而在Ｐ４５０ⅢＡ对２，４，５－ＴＦＡ降解为ＣＯ中或许起主要作用，为证实这一推论，我们研究了ＣＯ生成能力与Ｐ４５０不同亚族的特征催化活性间的相关性。在所选用的红霉素氮上去甲基化，三乙酰竹桃霉素（ＴＡＯ）代谢中间体（ＭＩ）络合物生成能力，对氨基苯甲酸叔丁酯ＭＩ络合物生成能力，戊氧基异吩唑氧上去烷基化，乙氧基异吩唑氧上去乙基化，以及氨基比林氮上去甲基化等活性指标中，仅表征Ｐ４５０ⅢＡ的活性指标──ＴＡＯ－ＭＩ络合物生成能力及红霉素氮上去甲基酶活性，与ＣＯ的生成能力明显相关。给ＤＥＸ诱导的大鼠以Ｐ４５０ⅢＡ的抑制剂ＴＡＯ处理，鼠肝微粒体的Ｐ４５０含量，ＴＡＯ－ＭＩ络合物生成能力，红霉素氮上去甲基化作用，及ＣＯ生成能力的丢失程度相近。上述结果表明，Ｐ４５０Ⅲ?     

2，4，5－三氟苯甲酸合成路线图解

２，４，５－三氟苯甲酸合成路线图解张跃臻（阜新市化工研究所，辽宁１２３０００）ＧＲＡＰＨＩＣＡＬＳＹＮＴＨＥＴＩＣＲＯＵＴＥＳＯＦ２，４，５－ＴＲＩＦＬＵＯＲＯＢＥＮＺＯＩＣＡＣＩＤ￥ＺＨＡＮＧＹｕｅｎ－Ｚｈｅｎ（ＦｕｘｉｎＩｎｓｔｉｔｕｔｅｏｆＣｈ...     

2，2，6，6－四氯环己酮的制备

２，２，６，６－四氯环己酮的制备叶发青，周和平（咸宁医学院，湖北４３７１００）ＰＲＥＰＡＲＡＴＩＯＮＯＦ２，２．６，６－ＴＥＴＲＡＣＨＬＯＲＯＣＹＣＬＯＨＥＸＡＮＯＮＥ￥ＹＥＦａ－Ｑｉｎｇ，ＺＨＯＵＨｅ－Ｐｉｎｇ（ＸｉａｎｎｉｎｇＭｅｄｉｃａｌＣｏｌ...     

（4R）—2,2—二甲基—1,3—二氧戊环—4—羧酸甲酯的制备

（４Ｒ）┐２，２┐二甲基┐１，３┐二氧戊环┐４┐羧酸甲酯的制备ＰＲＥＰＡＲＡＴＩＯＮＯＦＭＥＴＨＹＬ（４Ｒ）┐２，２┐ＤＩＭＥＴＨＹＬ┐１，３┐ＤＩＯＸＯＬＡＮＥ┐４┐ＣＡＲＢＯＸＹＬＡＴＥ赵军（浙江工业大学化学工程学院，杭州３１００３２）ＺＨＡＯＪ...     

2，6－二叔丁基－4－硫氰基苯酚的合成

２，６－二叔丁基－４－硫氰基苯酚的合成王松青，刘秀杰（沈阳药科大学化学制药教研室，辽宁１１００１５）ＳＹＮＴＨＥＳＩＳＯＦ２，６－ＤＩ－ｔｅｒｔ－ＢＵＴＹＬ－４－ＴＨＩＯＣＹＡＮＡＴＯＰＨＥＮＯＬ￥ＷＡＮＧＳｏｎｇ－Ｑｉｎｇ；ＬＩＵＸｉｕ－Ｊｉｅ（Ｓ...     

原发性肺动脉高压患者的运动心肺功能（附二例报告）

报告２例经心导管检查证实为原发性肺动脉高压的女性患者运动心肺功能改变特点。其ＰＡ及ｍＰＡ分别为１０／４．７ｋＰａ、６．５ｋＰａ及９．７／３．６ｋＰａ、５．３ｋＰａ。１．Ｖ／Ｑ比率失调、气体交换异常，表现为低氧血症，Ｐ（Ａ－ａ）Ｏ２异常增宽，ＶＤ／ＶＴ增加以及Ｐ（ａ－ｅｔ）ＣＯ２为正值；２．心输量减低导致ＶＯ２ｍａｘ、ＡＴ及（ＣＯ２／ＨＲ）ｍａｘ减低；３．通气储备ＢＲｍａｘ及ＤＩｍａｘ正常，但于ＡＴ     

氧代赖氨酸对肝癌细胞生长、AFP分泌及γ-GT活性的抑制作用

目的研究氧代赖氨酸（Ｌ ４ ｏｘａｌｙｓｉｎｅ，ＯＸＬ）对人肝癌细胞体内、外生长及其对甲胎蛋白（ＡＦＰ）分泌和γ 谷氨酰转肽酶（γ ＧＴ）活性的影响。方法以ＭＴＴ法测定ＯＸＬ的体外抗肝癌活性。以裸小鼠异种移植人肝癌模型观察药物的体内抗肝癌作用。以酶联免疫法（ＥＬＩＳＡ）检测ＡＦＰ水平。以酶底物法检测γ ＧＴ活力。结果①ＯＸＬ０８～６８×１０－４ｍｏｌ·Ｌ－１作用６ｄ，对体外培养的３种人肝癌ＨｅｐＧ２、Ｂｅｌ ７４０２和Ｂｅｌ ７４０４细胞株仅有微弱的生长抑制作用，６８×１０－４ｍｏｌ·Ｌ－１时的抑制率为１３７％～４５６％。②ＯＸＬ２００ｍｇ·ｋｇ－１，ｐｏ，ｑｄ×２ｗｋ对裸小鼠异种移植人ＨＣＣ ９３实体型肝癌的生长有明显抑制作用，抑瘤率为４３５％（Ｐ＜００５）。③ＯＸＬ能明显抑制人肝癌细胞ＡＦＰ分泌量和γ ＧＴ酶活力，丝裂霉素Ｃ在治疗剂量时能明显抑制人肝癌的生长，并使γ ＧＴ的活性显著降低，但对ＡＦＰ的抑制作用却较弱。结论ＯＸＬ的体内抗人肝癌活性较体外强，其作用与１９９８ ０６ ２４收稿，１９９８ １１ １８修回国家自然科学基金资助项目，Ｎｏ３９５７０８２４作者简介：章雄文，男，３４岁，博士?     

吡喹酮对映异构体在诱导和未诱导大鼠肝微粒体内代谢的立体选择性

吡喹酮（ＰＱＴ）对映异构体在未诱导大鼠肝微粒体内仅（－）ＰＱＴ生成一个主要代谢产物－ＲｉｎｇＤ－ＯＨ，而在β－萘黄酮（β－ＮＦ）诱导的大鼠肝微粒体内两者均生成ＲｉｎｇＤ－ＯＨ．（＋）ＰＱＴ在苯巴比妥（ＰＢ）诱导的肝微粒体内可生成三个主要代谢物，即ＲｉｎｇＤ－ＯＨ，ＲｉｎｇＢ－ＯＨ和ＲｉｎｇＡ－ＯＨ，而（－）ＰＱＴ仅生成ＲｉｎｇＤ－ＯＨ和ＲｉｎｇＡ－ＯＨ．在地塞米松（ＤＥＸ）诱导的大鼠肝微粒体内，ＰＱＴ对映异构体代谢后生成四个主要产物，除ＲｉｎｇＤ－ＯＨ，ＲｉｎｇＢ－ＯＨ和ＲｉｎｇＡ－ＯＨ外，尚有ＲｉｎｇＤ，Ｂ－２ＯＨ．ＰＱＴ对映异构体无论在β－ＮＦ，ＰＢ或ＤＥＸ诱导的肝微粒体内，ＲｉｎｇＤ－ＯＨ的生成速率均为（－）ＰＱＴ大于（＋）ＰＱＴ，ＲｉｎｇＢ－ＯＨ和ＲｉｎｇＡ－ＯＨ的生成均为（＋）ＰＱＴ较（－）ＰＱＴ优先被羟化．本实验结果表明，β－ＮＦ，ＰＢ和ＤＥＸ所诱导的ＣＹＰ１Ａ，ＣＹＰ２Ｂ和ＣＹＰ３Ａ及未诱导Ｐ４５０代谢ＰＱＴ对映异构体表现出完全的或部分的立体选择性．     

甲基莲心碱在大鼠肝微粒体CYP450系统中的代谢特征

目的研究甲基莲心碱(Nef)在大鼠肝微粒体系的代谢特性,探明参与Nef代谢的CYP450亚酶种类及其在Nef代谢中的作用。方法应用CYP3A特异性诱导剂地塞米松(DEX)、CYP2B诱导剂苯巴比妥(PB)、CYP1A诱导剂β-萘黄酮(β-NF)分别对W istar大鼠进行在体诱导,建立肝微粒体温孵及NADPH再生体系,HPLC紫外检测法测定Nef及其代谢产物。观察Nef代谢消失率与代谢特征,研究上述各诱导剂和CYP3A特异性抑制剂三乙酰竹桃霉素(TAO)对Nef体外代谢的影响。结果Nef在大鼠微粒体系代谢呈饱和现象;温孵液中代谢产物生成的量与底物Nef的浓度具有良好的相关性(r=0.993);Nef在DEX、PB诱导组大鼠肝微粒体温孵液中的生物转化较对照组明显加快(P<0.01),DEX组又较PB组的Nef药物代谢率差异有显著性(P<0.01),而β-NF组未显现诱导作用,其药物代谢率分别为:DEX组80.6%±9.5%;PB组61.5%±6.7%;β-NF组20.7%±1.5%;对照组19.9%±1.6%;TAO呈量效依赖性抑制Nef在肝微粒体温孵液中的代谢。结论研究结果提示Nef具有酶促动力学代谢特性;CYP3A及CYP2B是介导Nef在大鼠体内生物转化的CYP450亚酶,其中主要参与Nef代谢的为CYP3A。     

银杏黄酮山奈酚的体外葡醛酸结合反应

目的　旨在了解银杏黄酮山奈酚代谢的有关酶系及酶动力学参数。方法　采用苯巴比妥 (PB)、地塞米松 (DEX)、β 萘黄酮 (BNF)和地非三唑 (DIPH)诱导SD大鼠 ,与未诱导大鼠分别作为体外代谢的 5种不同酶源。取山奈酚和鼠肝微粒体 2 5℃下共孵育 ,HPLC法测定孵育液中剩余底物浓度。比较不同诱导剂处理的鼠肝微粒体对山奈酚代谢的催化活性 ,以未作任何处理的鼠肝微粒体为空白对照。结果　山奈酚在BNF和DIPH诱导的鼠肝微粒体中有较强的代谢作用 ,而在PB ,DEX诱导的鼠肝微粒体和空白组微粒体中的代谢较弱。在 0 .2g·L- 1的微粒体蛋白质浓度的孵育液中 ,山奈酚 (40mg·L- 1)经4 5min孵育后 ,分别有 6 2 .9% (DIPH ) ,4 0 .1%(BNF) ,2 1.1% (PB) ,2 3.7% (DEX)和 18.0 % (空白组 )的量被代谢。测得山奈酚在空白对照组、BNF和DIPH诱导的微粒体中的Km 值分别为 (1.85±1.0 5 ) ,(9.4 1± 2 .4 5 )和 (72 .4± 3.0 8) μmol·L- 1;Vmax值分别为 (2 .4 5± 0 .6 3) ,(7.5 5± 1.4 0 )和 (2 5 .2±1.0 8) μmol·g- 1·min- 1。结论　山奈酚在各种微粒体中被广泛代谢 ;BNF和DIPH葡醛酸转移酶的强诱导剂可使山奈酚Ⅱ相葡萄糖醛酸苷结合反应增强。     

吡喹酮对映异构体在诱导和未诱导大鼠肝微粒体内代谢的立体选择性

吡喹酮（PQT）对映异构体在未诱导大鼠?肝微粒体内仅（-）PQT生成一个主要代谢产物－Ring D-OH，而在β-萘黄酮（β－NF）诱导的大鼠肝微粒体内两者均生成#FSRing D-OH. (+)PQT在苯巴比妥（PB）诱导的肝微粒体内可生成三个主要代谢物，即Ring D-OH, Ring B-OH和Ring A-OH，而(-)PQT仅生成Ring D-OH和Ring A-OH. 在地塞米松(DEX)诱导的大鼠肝微粒体内，PQT对映异构体代谢后生成四个主要产物，除Ring D-OH, Ring B-OH和Ring A-OH外，尚有Ring D，B－2OH. PQT对映异构体无论在β-NF, PB或DEX诱导的肝微粒体内，Ring D-OH的生成速率均为(-)PQT大于(+)PQT, Ring B-OH和Ring A-OH的生成均为(+)PQT较(-)PQT优先被羟化. 本实验结果表明，β-NF, PB和DEX所诱导的CYP1A, CYP2B和CYP3A及未诱导P450代谢PQT对映异构体表现出完全的或部分的立体选择性.     

Effects of a series of 4-alkyl analogues of 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine on the major inducible cytochrome P-450 isozymes of rat liver

Various 4-alkyl analogues of 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine (DDC) cause mechanism-based inactivation of cytochrome P-450 (P-450) by destroying the heme prosthetic group. We have examined the isozyme selectivity of representative DDC analogues with respect to the major inducible P-450 isozymes of rat liver. Hepatic microsomes from untreated, phenobarbital (PB)-treated, beta-naphthoflavone (beta NF)-treated, and dexamethasone (DEX)-treated rats were incubated with a DDC analogue and NADPH and were subsequently analyzed for P-450 and heme content, P-450 isozyme immunoreactivity, and enzyme activity. Compared with the uninduced state, 4-isopropyl-DDC caused slightly less P-450 destruction following beta NF induction and much greater destruction following DEX pretreatment. Also, 4-hexyl-DDC was found to cause less P-450 destruction following PB or DEX pretreatment, compared with results obtained with untreated rats. These results suggest that DDC analogues possess different isozyme selectivity profiles. Monoclonal antibodies (MAbs) directed against the major inducible isozymes of P-450 were used to probe Western blots of microsomal protein following DDC analogue treatment. The formation of lower molecular mass (45-55 kDa) immunoreactive proteins in microsomes from beta NF-treated rats following DDC analogue treatment was revealed by two MAbs (1-31-2 and 1-36-1), suggesting that the apoprotein of the major beta NF-inducible isozyme, P-450c, is subject to alteration by DDC analogues. In microsomes from DEX-treated rats, DDC analogues caused the formation of higher molecular mass (80, 94, and 115 kDa) proteins showing immunoreactivity with MAb 2-13-1, directed against a major DEX-inducible isozyme belonging to the P-450p family. These immunochemical findings are supported by the demonstration that DDC analogues also caused mechanism-based inhibition of the catalytic activity of P-450c (7-ethoxyresorufin O-deethylase) and P-450p (erythromycin N-demethylase) but not that of the major PB-inducible isozyme, P-450b (7-pentoxyresorufin O-dealkylase). The combined immunochemical and enzymic studies indicate that rat liver P-450 c and p are targets for mechanism-based inactivation by DDC analogues.     

CYP isoform induction screening in 96-well plates: use of 7-benzyloxy-4-trifluoromethylcoumarin as a substrate for studies with rat hepatocytes

1. In this study, 7-benzyloxy-4-trifluoromethylcoumarin (BFC) was evaluated as a substrate to assess the induction of cytochrome P450 (CYP) isoform enzyme activities in rat hepatocytes using a 96-well plate format. 2. BFC was metabolized by both untreated and sodium phenobarbitone (NaPB)-treated rat hepatocytes in a time- and concentration-dependent manner to the highly fluorescent product 7-hydroxy-4-trifluoromethylcoumarin (HFC). 3. HFC was extensively conjugated with D-glucuronic acid and/or sulphate in both untreated and NaPB-treated rat hepatocytes, thus necessitating the inclusion of an enzymatic deconjugation step in the assay procedure. 4. The time-course of induction of 7-ethoxyresorufin metabolism by the CYP1A inducer beta-naphthoflavone (BNF), 7-benzyloxyresorufin metabolism by the CYP2B inducer NaPB and BFC metabolism b both BNF and NaPB was studied in rat hepatocytes treated for 24-96 h. The optimal time for induction of metabolism of all three substrates was 72 h, with no medium changes being necessary during this period. 5. The effect of treatment with 0.5-20 microM BNF, 50-2000 microM NaPB, 2-20 microM dexamethasone (DEX), 20-100 microM methylclofenapate (MCP), and 50 and 200 microM isoniazid (ISN) for 72 h on BFC metabolism in cultured rat hepatocytes was studied. BFC metabolism was induced by treatment with BNF, NaPB and MCP, but not with either DEX or ISN. 6. The metabolism of BFC in liver microsomes from the control rat and rat treated with CYP isoform inducers was also studied. BFC metabolism was induced by treatment with NaPB, BNF and DEX. 7. The metabolism of BFC was also studied using microsomes from baculovirus-infected insect cells containing rat cDNA-expressed CYP1A, CYP2B, CYP2C and CYP3A isoforms. Whereas BFC was metabolized to some extent by all the rat cDNA-expressed CYP isoforms examined, at a substrate concentration of 2.5 microM the greatest rates of BFC metabolism were observed with the CYP1A1, CYP1A2 and CYP2B1 preparations. 8. In summary, the results demonstrate that BFC is a good substrate for assessing the induction of CYP1A and CYP2B isoforms in rat hepatocytes in a 96-well plate format.     

吡喹酮在诱导和未诱导大鼠肝微粒体内的羟化代谢概貌及其羟化物的质谱鉴定

用细胞色素P450（P450）特异诱导剂研?究参与吡喹酮（PQT）代谢的P450同工酶，在未诱导肝微粒体内，PQT代谢仅生成其D环单羟化物. 在β-萘黄酮诱导肝微粒体内，PQT代谢后也生成其D环单羟化物. PQT在苯巴比妥诱导的肝微粒体内代谢生成D环，B环和A环三个单羟化物. 在地塞米松和红霉素诱导的肝微粒体内，PQT代谢生成七个代谢产物. 结果表明参与PQT分子羟化的P450同工酶至少包括CYP1A，CYP2B和CYP3A亚家族，每个亚家族代谢PQT的概貌各不相同，CYP3A优先羟化A环，CYP2B优先羟化D环和B环，CYP1A则几乎仅羟化D环.     

Rat hepatic microsomal metabolism of ethylenethiourea. Contributions of the flavin-containing monooxygenase and cytochrome P-450 isozymes

The contributions of the rat hepatic flavin-containing monooxygenase (FMO) and cytochrome P-450 isozymes (P-450) in the ethylenethiourea (ETU) mediated inactivation of P-450 isozymes and covalent binding of the compound to microsomal proteins were investigated. In vitro, ETU was found to inhibit P-450 marker activities in microsomes obtained from untreated (UT) and phenobarbital (PB), beta-naphthoflavone (BNF), and dexamethasone (DEX) pretreated rats. This inhibition was dependent on the presence of NADPH and was completely abolished by coincubation with glutathione (GSH). Heat treatment of microsomes prior to ETU-mediated P-450 inactivation led to diminished loss of P-450 marker activities in microsomes obtained from UT and PB-pretreated, but not BNF- or DEX-pretreated rats, suggesting FMO involvement in the inactivation of some P-450 isozymes. Covalent binding of [14C]ETU to microsomal proteins was found to be NADPH-dependent and enhanced with BNF or DEX pretreatment of rats. This binding was completely inhibited by coincubation with GSH. Heat treatment of microsomes and P-450 inactivation studies indicated a predominant role of FMO in the observed covalent binding. Addition of the sulfhydryl reagents dithiothreitol (DTT) or GSH after the incubation of microsomes, [14C]ETU, and NADPH resulted in the complete release of bound ETU, suggesting the reduction of disulfide bonds between oxidized ETU and protein sulfhydryls. Microsomal heme content was not decreased following incubation of microsomes with ETU and NADPH, and P-450 appeared to be converted to P-420.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of 7-benzyloxy-4-trifluoromethylcoumarin, some other 7-hydroxy-4-trifluoromethylcoumarin derivatives and 7-benzyloxyquinoline as fluorescent substrates for rat hepatic cytochrome P450 enzymes.

1. The aim of this study was to evaluate a number of derivatives of 7-hydroxy-4-trifluoromethylcoumarin (HFC) and 7-benzyloxyquinoline (7BQ) as novel fluorescent substrates for monitoring rat hepatic cytochrome P450 (CYP) enzyme specificity in a 96- well plate format. The HFC derivatives examined comprised 7-benzyloxy-4-trifluoromethylcoumarin (BFC), 2,5-bis(trifluoromethyl)-7-benzyloxy-4-trifluoromethylcoumarin (BFBFC), 3,5-bis(trifluoromethyl)-7-benzyloxy-4-trifluoromethylcoumarin (BTBFC), 2-(trifluoromethyl)-7-benzyloxy-4-trifluoromethylcoumarin (2TFBFC), 3-(trifluoromethyl)-7-benzyloxy-4-trifluoromethylcoumarin (3TFBFC) and 3-(trifluoromethoxy)-7-benzyloxy-4-trifluoromethylcoumarin (3TFMeOBFC). 2. The CYP specificity of the fluorescent probe substrates was examined using characterized liver microsomes from male Sprague-Dawley rats treated with beta naphthoflavone (BNF), sodium phenobarbitone (NaPB), isoniazid, pregnenolone-16alpha-carbonitrile (PCN), dexamethasone (DEX) and methylclofenapate to induce CYP1A, CYP2B, CYP2E, CYP3A, CYP3A and CYP4A forms, respectively. Studies were also performed with microsomes from baculovirus-infected insect cells containing rat cDNA-expressed CYP1A1, CYP1A2, CYP2B1, CYP3A1 and CYP3A2. 3. BFC metabolism was most markedly induced by BNF and NaPB, whereas BFBFC metabolism was most markedly induced by PCN and DEX and BTBFC was not metabolized by rat liver microsomes. BFC was a high-affinity substrate for cDNA-expressed CYP1A1 and CYP2B1, whereas BFBFC exhibited a high affinity for CYP3A1 and CYP3A2. 4. The metabolism of 2TFBFC and 3TFBFC was induced by NaPB, PCN and DEX. 3TFBFC was a relatively specific substrate for cDNA-expressed CYP2B1, whereas 2TFBFC could be metabolized by CYP2B1, CYP3A1 and CYP3A2. 5. 3TFMeOBFC metabolism was markedly induced by BNF treatment and 3TFMeOBFC was extensively metabolized by cDNA-expressed CYP1A1. 6. The metabolism of 7BQ to 7-hydroxyquinoline was induced by treatment with PCN and DEX. 7BQ was a substrate for cDNA-expressed CYP3A2 and to a lesser extent for CYP3A1. 7. In summary, some of the HFC derivatives studied and 7BQ are useful fluorescent probe substrates for rat CYP enzymes. BFC appears to be a probe for CYP1A and CYP2B, 2TFBFC for CYP2B and CYP3A and 3TFBFC for CYP2B. While 3TFMeOBFC appears to be a relatively specific probe for CYP1A1, both BFBFC and 7BQ are good probes for the induction of CYP3A.     

Ontogeny of the chicken cytochrome P-450 enzyme system. Expression and development of responsiveness to phenobarbital induction

The sensitivity of the developing embryo to toxins and drugs is highly dependent on the state of development of the cytochrome P-450 system. Previous work in this laboratory has demonstrated the genotoxicity of aflatoxin B1 (AFB1) to the chicken embryo at 3 days of incubation (DI) and induction of AFB1 genotoxicity by phenobarbital at 7 DI. In this study, the basal and 24-hr phenobarbital (PB) induced levels of aminopyrine-N-demethylase (AMPD) and cytochrome P-450 were assayed in hepatic microsomes from 7 DI to 36 days posthatching (PH) and in microsomes from whole embryos at 5 DI. A dose-response for induction by PB was observed in embryonic hepatic microsomes as early as 7 DI, whereas a low level of cytochrome P-450 was detected in control 7 DI microsomes using the reduced CO vs oxidized CO difference spectrum. Basal levels of AMPD and cytochrome P-450 in hepatic microsomes increased steadily throughout development as did the responsiveness of the embryonic liver to induction with PB. Hepatic microsomes from control and PB-induced chickens had the highest AMPD activities posthatching particularly from 1 to 3 days PH. Maximal induced levels, which were 2- to 3-fold over control throughout development, ranged from 1.22 at 7 DI to 12.72 nmol HCHO/mg protein/min at 2 days PH. The potency of PB as an inducer increased about 1000-fold between 7 DI and hatching. PB induction did not increase the specific activity of AMPD at any period of development. The specific activity of AMPD posthatching increased about 3-fold above embryonic levels, indicating the development of a cytochrome P-450 complex more active toward aminopyrine in the neonatal period.