Catalytic and immunochemical characterization of hepatic microsomal cytochromes P450 in beluga whale (Delphinapterus leucas).
Catalytic and immunochemical characterization of hepatic microsomal cytochromes P450 in beluga whale (Delphinapterus leucas).
复制标题
白鲸 (Delphinapterus leucas) 肝微粒体细胞色素 P450 的催化和免疫化学特征。
DOI：
10.1006/taap.1994.1089
复制
发表时间：
1994
影响因子：
3.8
通讯作者：
Stegeman,JJ
中科院分区：
文献类型：
--
作者：
White,RD;Hahn,ME;Lockhart,WL;Stegeman,JJ
了解环境污染物对鲸目动物和其他海洋哺乳动物的影响需要有关这些物种的外源代谢的生物化学信息。我们对来自加拿大北极地区的白鲸 (Delphinapterus leucas) 的肝微粒体细胞色素 P450 系统进行了表征。女性和男性的天然P450含量平均为0.203和0.319 nmol/mg微粒体蛋白，细胞色素b5含量平均为0.199和0.236 nmol/mg，NADPH-细胞色素c还原酶速率分别为79和76 nmol/min/mg。乙氧基试卤灵 O-脱乙基酶 (EROD)、戊氧基试卤灵 O-脱戊基酶 (PROD) 和苯并[a]芘 (BP) 羟化酶 (AHH) 活性在男性中显着高于女性，并且彼此高度相关（r2 在 0.853 和 0.912 之间）。体外 BP 代谢物的 HPLC 分析显示苯并环（7,8-和 9,10-）二氢二醇（与该化合物的活化一致）以及 4,5-二氢二醇、3-OH-、7-OH-和 9-OH-BP 以及 1,6- 和 3,6-醌。雌二醇2-羟化酶活性在性别之间没有差异，并且比率与其他活性的比率不相关。针对 scup P450B（一种明显的硬骨鱼 CYP2B）和大鼠 CYP2B1 的抗体无法识别白鲸肝微粒体中的蛋白质，但针对 PB 诱导型兔 CYP2B4 的抗体检测到了一种蛋白质。乙醇和酮诱导型大鼠 CYP2E1 的抗体与白鲸肝微粒体中的两种蛋白质发生反应。碳氢化合物诱导型 CYP1A1 和/或 CYP1A2 形式的特异性抗体显示出单一蛋白带，显然与 CYP1A1 关系更密切。雄性白鲸的 CYP1A 含量是雌性白鲸的五倍。 CYP1A 含量与 EROD、PROD 和 AHH 活性高度相关，表明这种 P450 形式是白鲸中这些反应的主要催化剂。 CYP1A 含量和活性与非邻位和单邻位 PCB 同系物（在其他哺乳动物中诱导 CYP1A 的化合物）的脂肪浓度高度相关。这些结果表明 CYP1A 是白鲸体内芳香烃污染物代谢的催化剂，并强烈表明这种蛋白质是由环境污染物（包括多氯联苯）在这些生物体中诱导产生的。结果支持测量 CYP1A 表达作为海洋哺乳动物暴露于诱导剂的生物标志物。白鲸 CYP1A 以及与其他 P450 形式免疫相关的白鲸蛋白的完整功能和进化关系尚不确定。
Understanding the effects of environmental contaminants on cetaceans and other marine mammals will require information on the biochemistry of xenobiotic metabolism in these species. We characterized the hepatic microsomal cytochrome P450 system in beluga whales (Delphinapterus leucas) from the Canadian Arctic. The content of native P450 averaged 0.203 and 0.319 nmol/mg microsomal protein, cytochrome b5 content averaged 0.199 and 0.236 nmol/mg, and rates of NADPH-cytochrome c reductase were 79 and 76 nmol/min/mg, for females and males respectively. Ethoxyresorufin O-deethylase (EROD), pentoxyresorufin O-depentylase (PROD), and benzo[a]pyrene (BP) hydroxylase (AHH) activities were significantly greater in males than in females, and were highly correlated with one another (r2between 0.853 and 0.912). HPLC analysis of in vitro BP metabolites revealed benzo-ring (7,8- and 9,10-) dihydrodiols, consistent with activation of this compound, as well as 4,5-dihydrodiol,3-OH-, 7-OH-, and 9-OH-BP and 1,6- and 3,6-quinones. Estradiol 2-hydroxylase activity did not differ between sexes, and rates did not correlate with those of the other activities. Antibodies against scup P450B (an apparent teleost CYP2B) and rat CYP2B1 did not recognize proteins in beluga liver microsomes, but there was a protein detected by antibodies to PB-inducible rabbit CYP2B4. Antibodies to ethanol and ketone-inducible rat CYP2E1 reacted with two proteins in beluga liver microsomes. Antibodies specific to hydrocarbon-inducible CYP1A1 and/or CYP1A2 forms showed a single protein band, apparently more closely related to CYP1A1. The content of CYP1A was fivefold greater in male than in female beluga. CYP1A content was highly correlated with EROD, PROD, and AHH activities, suggesting that this P450 form is a primary catalyst for these reactions in beluga. CYP1A content and activity were highly correlated with the concentrations in blubber of non-ortho and mono-ortho PCB congeners, compounds that induce CYP1A in other mammals. These results indicate that a CYP1A is a catalyst for the metabolism of aromatic hydrocarbon pollutants in the beluga whale, and strongly suggest that this protein is induced in these organisms by environmental contaminants, including PCBs. The results support the measurement of CYP1A expression as a biomarker of exposure to inducers in marine mammals. The full functional and evolutionary relationships of beluga CYP1A and of beluga proteins immunologically related to other P450 forms are uncertain.