Reddy M V, Randerath K
Department of Pharmacology, Baylor College of Medicine, Texas Medical Center, Houston 77030.
Mutat Res. 1990 May;241(1):37-48. doi: 10.1016/0165-1218(90)90107-d.
Measurement of tissue/cell DNA adducts represents a suitable monitor of carcinogen exposure because the majority of chemical mutagens/carcinogens react with DNA, forming covalent adducts, a key event in the initiation of chemical carcinogenesis. Investigations of DNA-adduct formation in vivo in white blood cells (WBC) versus target tissues, i.e. internal organs for most carcinogens, is expected to yield useful information about the suitability of WBC for biomonitoring and risk assessment. For this purpose, female ICR mice were given 0.4 mmole/kg benzo[a]pyrene (BP), 0.045 mmole/kg dibenzo[c,g]carbazole (DBC) or 2.47 mmole/kg safrole by oral gavage or 4 daily doses (equivalent to 3 cigarettes) of cigarette-smoke condensate (CSC) by topical application. At 24 h after dosing, DNA adducts were detected by a nuclease P1-enhanced 32P-postlabeling assay [M.V. Reddy and K. Randerath, Carcinogenesis, 7 (1986) 1543] in WBC and internal tissues treated with individual carcinogens, while CSC treatment elicited aromatic adducts in most tissues but not in WBC. Adduct patterns of WBC DNA were qualitatively similar to those of internal organs, but adduct amounts varied. BP, a systemic carcinogen, bound nearly as much to WBC DNA as to target-tissue DNA samples; whereas the liver carcinogens, DBC and safrole, bound to WBC DNA considerably less (22- and 51-fold, respectively) compared with liver DNA. The number of adducts in 10(7) nucleotides of WBC, liver, lung, kidney and spleen DNA, respectively, were: 2, 5, 3, 2 and 3 with BP; 6, 131, 6, 14 and 4 with DBC; 5, 238, 3, 5 and 0.6 with safrole. For CSC, these values were 0, 1 and 0.02 in WBC, lung and spleen, respectively. Our results show that carcinogen binding to WBC DNA does not reflect binding to target-tissue DNA in a quantitative sense for the carcinogens studied except for BP, and that WBC are not suitable surrogates for monitoring CSC exposure by DNA-adduct measurement after topical application. The CSC data in mice was consistent with the previous findings in humans that smokers' tissues but not WBC show smoking-related bulky/aromatic DNA adducts, as measured by 32P-postlabeling.
组织/细胞DNA加合物的测量是监测致癌物暴露的合适方法，因为大多数化学诱变剂/致癌物会与DNA发生反应，形成共价加合物，这是化学致癌作用起始过程中的关键事件。研究白细胞（WBC）与靶组织（即大多数致癌物的内部器官）中体内DNA加合物的形成情况，有望获得有关白细胞用于生物监测和风险评估适用性的有用信息。为此，给雌性ICR小鼠经口灌胃给予0.4毫摩尔/千克苯并[a]芘（BP）、0.045毫摩尔/千克二苯并[c,g]咔唑（DBC）或2.47毫摩尔/千克黄樟素，或通过局部涂抹给予4剂每日剂量（相当于3支香烟）的香烟烟雾冷凝物（CSC）。给药后24小时，通过核酸酶P1增强的32P后标记测定法[M.V.雷迪和K.兰德拉斯，《癌变》，7（1986年）1543]在经单个致癌物处理的白细胞和内部组织中检测DNA加合物，而CSC处理在大多数组织中引发芳香族加合物，但在白细胞中未引发。白细胞DNA的加合物模式在质量上与内部器官相似，但加合物数量有所不同。BP是一种全身性致癌物，与白细胞DNA的结合量几乎与靶组织DNA样本相同；而肝脏致癌物DBC和黄樟素与白细胞DNA相比，与肝脏DNA的结合量要少得多（分别为22倍和51倍）。白细胞、肝脏、肺、肾和脾DNA中每10（7）个核苷酸的加合物数量分别为：BP处理时为2、5、3、2和3；DBC处理时为6、131、6、14和4；黄樟素处理时为5、238、3、5和0.6。对于CSC，白细胞、肺和脾中的这些值分别为0、1和0.02。我们的结果表明，除BP外，对于所研究的致癌物，致癌物与白细胞DNA的结合在定量意义上并不反映与靶组织DNA的结合，并且白细胞不适用于通过局部涂抹后测量DNA加合物来监测CSC暴露。小鼠中的CSC数据与先前在人类中的发现一致，即通过32P后标记测量，吸烟者的组织而非白细胞显示出与吸烟相关的大体积/芳香族DNA加合物。
