Bullock P, Pearce R, Draper A, Podval J, Bracken W, Veltman J, Thomas P, Parkinson A
Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City 66160-7417, USA.
Drug Metab Dispos. 1995 Jul;23(7):736-48.
The aim of this study was to determine whether treatment of cynomolgus monkeys (Macaca fasicularis) with phenobarbital, beta-naphthoflavone, or dexamethasone causes an induction of microsomal crytochrome P450 (CYP) enzymes that are structurally and functionally related to rat enzymes belonging to the CYP1A, CYP2B, and CYP3A gene families. Oral treatment of male and female monkeys with phenobarbital resulted in a marked induction of a protein recognized by antibody against rat CYP2B1, as determined by Western immunoblotting. This protein, presumably a CYP2B enzyme, was not detectable in untreated monkeys, and was modestly inducible by dexamethasone but not beta-naphthoflavone. Induction of this CYP2B enzyme by phenobarbital was associated with a relatively large increase (up to 5-fold) in the rate of testosterone 16 beta-hydroxylation. Antibody, against rat CYP2B1 markedly inhibited this reaction in liver microsomes from phenobarbital-treated monkeys, but not from control monkeys. Consequently, the antibody-inhibitable rate of testosterone 16 beta-hydroxylation increased 17-fold after treatment of monkeys with phenobarbital, which is comparable with the situation in rats. In contrast to the rat CYP2B enzymes, the monkey CYP2B enzyme had little or no capacity to convert testosterone to 16 alpha-hydroxytestosterone or androstenedione, and had negligible capacity to O-dealkylate 7-pentoxyresorufin and 7-benzyloxyresorufin. Oral treatment of male and female monkeys with beta-naphthoflavone resulted in a marked induction of a protein recognized by polyclonal and monoclonal antibodies against rat CYP1A1 or against both CYP1A1 and CYP1A2. This protein was apparently a mixture of CYP1A1 and CYP1A2, neither of which was readily detectable in liver microsomes from control monkeys or monkeys treated with phenobarbital or dexamethasone. Induction of monkey CYP1A1/2 was associated with a marked increase in the O-dealkylation of 7-methoxyresorufin (up to 65-fold), the O-dealkylation of 7-ethoxyresorufin (up to 30-fold), and the N3-demethylation of caffeine (up to 17-fold), but only a 2-fold increase in benzo[a]pyrene 3-hydroxylation. Polyclonal antibodies against CYP1A1 markedly inhibited the N3-demethylation of caffeine and the O-dealkylation of 7-methoxy- and 7-ethoxyresorufin by liver microsomes from beta-naphthoflavone-treated monkeys, and partially inhibited the 3-hydroxylation of benzo[a]pyrene, indicating that monkey CYP1A1 and/or CYP1A2, like the corresponding rat enzymes, can catalyze all four reactions. Treatment of monkeys with phenobarbital resulted in a 2- to 3-fold induction of a protein recognized by antibody against rat CYP3A1. This protein (CYP3A8 or an immunochemically related enzyme) was constitutively expressed in untreated monkeys of both sexes.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究的目的是确定用苯巴比妥、β-萘黄酮或地塞米松处理食蟹猴（猕猴）是否会诱导微粒体细胞色素P450（CYP）酶，这些酶在结构和功能上与属于CYP1A、CYP2B和CYP3A基因家族的大鼠酶相关。用苯巴比妥对雄性和雌性猴子进行口服治疗，通过蛋白质免疫印迹法测定，结果显示一种能被抗大鼠CYP2B1抗体识别的蛋白质有显著诱导。这种蛋白质可能是一种CYP2B酶，在未处理的猴子中无法检测到，用地塞米松可适度诱导，但用β-萘黄酮则不能。苯巴比妥对这种CYP2B酶的诱导与睾酮16β-羟基化速率相对大幅增加（高达5倍）相关。抗大鼠CYP2B1抗体在苯巴比妥处理的猴子肝脏微粒体中能显著抑制该反应，但在对照猴子的肝脏微粒体中则不能。因此，用苯巴比妥处理猴子后，抗体可抑制的睾酮16β-羟基化速率增加了17倍，这与大鼠的情况相当。与大鼠CYP2B酶不同，猴子CYP2B酶将睾酮转化为16α-羟基睾酮或雄烯二酮的能力很小或没有，对7-戊氧基试卤灵和7-苄氧基试卤灵进行O-脱烷基化的能力也可忽略不计。用β-萘黄酮对雄性和雌性猴子进行口服治疗，结果显示一种能被抗大鼠CYP1A1多克隆和单克隆抗体或同时被抗CYP1A1和CYP1A2抗体识别的蛋白质有显著诱导。这种蛋白质显然是CYP1A1和CYP1A2的混合物，在对照猴子或用苯巴比妥或地塞米松处理的猴子的肝脏微粒体中均不易检测到。猴子CYP1A1/2的诱导与7-甲氧基试卤灵的O-脱烷基化（高达65倍）、7-乙氧基试卤灵的O-脱烷基化（高达30倍）和咖啡因的N3-去甲基化（高达17倍）显著增加相关，但苯并[a]芘3-羟基化仅增加2倍。抗CYP1A1多克隆抗体显著抑制β-萘黄酮处理的猴子肝脏微粒体中咖啡因的N3-去甲基化以及7-甲氧基和7-乙氧基试卤灵的O-脱烷基化，并部分抑制苯并[a]芘的3-羟基化，这表明猴子CYP1A1和/或CYP1A2与相应的大鼠酶一样，能催化所有这四种反应。用苯巴比妥处理猴子导致一种能被抗大鼠CYP3A1抗体识别的蛋白质诱导2至3倍。这种蛋白质（CYP3A8或一种免疫化学相关酶）在未处理的雌雄猴子中均有组成性表达。（摘要截选至400字）
