ENVIRONMENTAL HYDRAZINES AND METHYLATION OF DNA GUANINE

联氨是一种具有肝脏和神经毒性的环境污染物。 和微弱的肝癌致癌性。服用中毒性剂量的联氨 对啮齿动物产生7-甲基鸟嘌呤和O6-甲基鸟嘌呤 靶器官DNA。提出了联氨和联氨的生成 衍生物是致癌的，因为联氨与内源性的 甲醛生成四甲酰三嗪和/或福尔马嗪，进而 被代谢成甲基化试剂。环境友好型联氨 化合物将在体内测试其诱导甲基化的能力 DNA鸟氨酸及其作为游离碱释放肼的能力；顺丁烯二酸 酰肼、3-氨基-1，2，4-三氮唑、甲酰肼、 2-羟乙基肼、异丙肼、异烟肼、烟酰胺、苯肼、 磺胺二甲基咪唑、磺胺甲氧基吡嗪、磺胺苯唑、呋喃唑酮、 呋喃妥因、呋喃西林、异烟肼、肼、乙酰唑胺和 给SD大鼠口服苯肼。 肼基甲酰胺、肼基组氨酸、福拉嗪和 四甲酰三氮唑也将接受测试。24小时后 甲基鸟嘌呤将从中性热和 肝、肾和肺DNA的温和酸性水解物经高纯度分离 荧光高效液相色谱(HLPC) 分光光度检测。联氨将用高效液相色谱仪测定为 从组织的酸性提取物中提取邻苯二甲肼。偶氮甲烷的形成， 将测定偶氮甲烷、甲基偶氮甲烷和甲基偶氮甲醇 通过在体外和体内啮齿动物系统中的高效液相色谱作为研究的第一步 联氨活化为a的生化途径的阐明 甲基化试剂。缩合产物的生成动力学 联氨和甲醛将在体内和体外研究啮齿动物 系统，特别注意酒精的作用和 乙醛脱氢酶在代谢中激活这些产物。脱氧核糖核酸 甲基肼-甲醛缩合产物的甲基化， 将测定1，4-二甲基六氢-1，2，4，5-四嗪。环境 甲醛和肝脏毒素(二甲基亚硝胺、 将对二乙基亚硝胺、四氯化碳和磷进行研究 因为他们有能力提高组织中的甲醛水平并增加 联氨诱导的DNA鸟氨酸甲基化。甲醛将会被 用高效液相色谱仪测定。联氨诱导的甲基化对血管内皮生长因子表达的影响 5-甲基胞嘧啶在DNA中的分布及其维持甲基化 对新生大鼠和部分肝切除大鼠的肝脏进行研究； DNA酶解物中5-甲基胞嘧啶的测定 高效液相色谱柱。拟议的研究将提供实验证据，以评估 环境中潜在的DNA损伤剂--肼类化合物及其研究进展 它们可能对人类健康构成致癌危害。

Hydrazine is an environmental contaminant which is hepato- and neurotoxic and weakly hepatocarcinogenic. Administration of toxic doses of hydrazine to rodents results in formation of 7-methylguanine and O6-methylguanine in target organ DNA. It is proposed that hydrazine and hydrazine-generating derivatives are carcinogenic because hydrazine reacts with endogenous formaldehyde to form tetraformyltrisazine and/or formalazine which in turn are metabolized to methylation agents. Environmentally important hydrazino compounds will be tested in vivo for their ability to induce methylation of DNA guanine and their ability to release hydrazine as the free base; maleic hydrazide, 3-amino-1,2,4-triazole, methylformylhydrazine, 2-hydroxyethylhydrazine, iproniazid, isocarboxazid, nialamide, phenelzine, sulfamethizole, sulfamethoxypyridazine, sulfaphenazole, furazolidone, nitrofurantoin, nitrofurazone, isoniazid, hydralazine, acetazolamide, and phenylhydrazine will be administered orally to Sprague Dawley rats. Hydrazinecarboxamide, hydrazinohistidine, formalazine, and tetraformyltrisazine will also be tested. Twenty-four hours later methylguanines will be quantitatively determined from neutral thermal and mild acid hydrolysates of liver, kidney, and lung DNA fractionated by high performance liquid chromatography (hlpc) with fluorescence spectrophotometric detection. Hydrazine will be measured by hplc as phthalhydrazine from acid extracts of tissue. Formation of azomethane, azoxymethane, methylazomethanol and methylazoxymethanol will be determined by hplc in in vitro and in vivo rodent systems as an initial step in the elucidation of biochemical pathways for the activation of hydrazine to a methylating agent. Kinetics of formation of condensation products of hydrazine and formaldehyde will be studied in in vivo and in vitro rodent systems, with particular attention given to the role of alcohol and aldehyde dehydrogenases in the metabolic activation of these products. DNA methylation by the monomethylhydrazine-formaldehyde condensation product, 1,4-dimethylhexahydro-1,2,4,5-tetrazine, will be determined. Environmental sources of formaldehyde and the hepatotoxins (dimethylnitrosamine, diethylnitrosamine, carbon tetrachloride, and phosphorus) will be studied for their ability to raise tissue formaldehyde levels and augment hydrazine-induced methylation of DNA guanine. Formaldehyde will be measured by hplc. The effect of hydrazine-induced methylation on the distribution of 5-methylcytosine in DNA and on maintenance methylation in liver of newborn and partially hepatectomized rats will be investigated; 5-methylcytosine will be determined from enzymic hydrolysates of DNA by hplc. The proposed studies will provide experimental evidence to evaluate environmental hydrazine compounds as potential DNA damaging agents and the carcinogenic hazard they may present to human health.