Srinivasan S, Glauert H P
Department of Nutrition and Food Science, University of Kentucky, Lexington 40506.
Carcinogenesis. 1990 Nov;11(11):2021-4. doi: 10.1093/carcin/11.11.2021.
The peroxisome proliferator ciprofibrate was tested for its ability to induce DNA damage in the form of 5-hydroxymethyl-2'-deoxyuridine (HMdU), an adduct that results from the reaction of thymine in DNA with hydroxyl radicals. In order to quantify HMdU, DNA containing [3H]thymidine of high specific activity had to be obtained. Since hepatocytes normally have a very low rate of DNA synthesis, rats were subjected to partial hepatectomy to stimulate DNA synthesis and then were administered [methyl-3H]thymidine by three p.o., i.p. or i.v. injections 20, 22 and 24 h after partial hepatectomy; or by slow infusion through the portal vein, starting 20 h after partial hepatectomy for 4 h. The specific activity of DNA in rats receiving [3H]thymidine through the portal vein was considerably higher than in rats receiving p.o., i.p. or i.v. injections. Rats were then exposed to various doses of gamma-irradiation after partial hepatectomy and infusion of [6-3H]thymidine through the portal vein. DNA from the liver was extracted, enzymatically hydrolyzed and analyzed by HPLC. The percentage of HMdU in DNA increased in a dose-dependent manner. Rats were then treated with the carcinogens 2-acetylaminofluorene (AAF) or diethylnitrosamine (DEN) in conjunction with partial hepatectomy and infusion of [methyl-3H]thymidine. There was an increase in HMdU formation after a single administration of DEN or AAF. Another group of rats was fed a diet containing the peroxisome proliferator ciprofibrate for 3 weeks. After partial hepatectomy and infusion of [6-3H]thymidine, these rats were fed the same ciprofibrate-containing diet for 2-4 more weeks. HMdU was detected in DNA at 2-4 weeks after [6-3H]thymidine infusion, but the level at 4 weeks was nearly 50% less than at 2 weeks. This study shows that oxidative DNA damage in the form of HMdU is induced in the liver by gamma-irradiation, DEN, AAF and peroxisome proliferation.
对过氧化物酶体增殖剂环丙贝特诱导DNA损伤的能力进行了测试，该损伤以5-羟甲基-2'-脱氧尿苷（HMdU）的形式存在，HMdU是DNA中的胸腺嘧啶与羟基自由基反应产生的一种加合物。为了定量HMdU，必须获得含有高比活度[3H]胸腺嘧啶核苷的DNA。由于肝细胞正常情况下DNA合成速率很低，因此对大鼠进行部分肝切除术以刺激DNA合成，然后在部分肝切除术后20、22和24小时通过口服、腹腔注射或静脉注射给予[甲基-3H]胸腺嘧啶核苷；或者在部分肝切除术后20小时开始通过门静脉缓慢输注4小时。通过门静脉接受[3H]胸腺嘧啶核苷的大鼠的DNA比活度显著高于接受口服、腹腔注射或静脉注射的大鼠。然后在部分肝切除和通过门静脉输注[6-3H]胸腺嘧啶核苷后，将大鼠暴露于不同剂量的γ射线照射。提取肝脏中的DNA，进行酶解并通过高效液相色谱法分析。DNA中HMdU的百分比呈剂量依赖性增加。然后将大鼠与部分肝切除术和输注[甲基-3H]胸腺嘧啶核苷一起用致癌物2-乙酰氨基芴（AAF）或二乙基亚硝胺（DEN）处理。单次给予DEN或AAF后，HMdU的形成增加。另一组大鼠喂食含有过氧化物酶体增殖剂环丙贝特的饮食3周。在部分肝切除和输注[6-3H]胸腺嘧啶核苷后，这些大鼠再喂食相同的含环丙贝特饮食2至4周。在输注[6-3H]胸腺嘧啶核苷后2至4周在DNA中检测到HMdU，但4周时的水平比2周时低近50%。这项研究表明，γ射线照射、DEN、AAF和过氧化物酶体增殖在肝脏中诱导以HMdU形式存在的氧化性DNA损伤。
