Kinetics of micronucleus induction and cytotoxicity caused by distinct antineoplastics and alkylating agents in vivo

This mini-review aims to compare the differences in the kinetics of the induction of micronucleated polychromatic erythrocytes (MN-PCE) and cytotoxicity by distinct antineoplastic and genotoxic agents in murine peripheral blood in vivo and to correlate these kinetics with the underlying processes. Comparisons were carried out using our previously obtained data with nominal doses causing similar levels of cytotoxicity, as measured in terms reduction of PCE. The aneuploidogens caused the most rapid induction of MN-PCEs and had the highest rates of cytotoxicity and genotoxicity. The promutagens cyclophosphamide and dimethylnitrosamine showed the most delayed responses and had the lowest genotoxic and cytotoxic efficiencies. DNA crosslinking agents had a similar delay of 4–5 h, greater than those of aneuploidogens, but differed in their cytotoxic and genotoxic efficiencies. Methylnitrosourea and 5-aza-cytidine caused greater delays than crosslinking agents. These delays can be due to the methylnitrosourea-mediated induction of formation of mono alkyl adducts which are interpreted as mismatches during DNA duplication, whereas 5-aza-cytidine requires incorporation into the DNA to induce breakage. This review allows us to conclude that the requirement for metabolic activation and the mechanisms of DNA breakage and of micronucleus induction are the main factors that affect the time of maximal MN-PCE induction.     

益气活血解毒化痰方对DMN诱导的大鼠肝纤维化的预防和治疗

目的观察益气活血解毒化痰方对二甲基亚硝胺(DMN)诱导的大鼠肝纤维化预防和治疗作用.方法 DMN诱导大鼠肝纤维化,分别于造模初及结束时灌服益气活血解毒化痰方,以重组人干扰素α2b肌肉注射对照.90d后测定血清谷草转氨酶(AST)、谷丙转氨酶(ALT)活性,总胆红素(TBil)、总蛋白(TP)、白蛋白(Alb)含量,放射免疫分析法测定层粘连蛋白(Laminin,LN)、Ⅳ型胶原(collagen TypeⅣ,Ⅳ-C)、透明质酸(Hyaluronic Acid,HA)、Ⅲ型前胶原(Procollagen Type Ⅲ,PC Ⅲ)含量,同时苏木素-伊红(HE)染色及苦味酸-天狼星红染色,光镜下观察肝细胞损伤及胶原纤维增生程度.结果益气活血解毒化痰方预防性给药,能明显降低DMN诱导肝纤维化大鼠AST、ALT活性及TBil含量(P＜0.05),提高TP、Alb含量(P＜0.05),降低LN含量(P＜0.05);造模结束后治疗性给药,明显降低Ⅳ-C、HA含量(P＜0.05);预防及治疗给药均改善肝细胞损伤及胶原纤维增生程度,预防性给药明显降低纤维化计分(P＜0.05).结论预防性及治疗性服用益气活血解毒化痰方,均抑制DMN诱导的大鼠肝纤维化,而预防性给药能更好地阻止肝纤维化的形成和发展.     

芪参益气滴丸对肝纤维化大鼠肝脏胶原表达的影响

目的：应用二甲基亚硝胺（DMN）建立肝纤维化大鼠模型，研究芪参益气滴丸对纤维化肝组织中Ⅰ、Ⅲ型胶原表达的影响。方法：70只大鼠随机分为正常对照组、模型组、芪参益气滴九干预组、模型对照组及芪参益气滴丸治疗组。采用DMN腹腔内注射的方法建立肝纤维化大鼠模型。按6期分类法评价各组大鼠肝纤维化程度。应用RT—PCR法检测各组大鼠肝组织中Ⅰ、Ⅲ型胶原mRNA水平；应用免疫组织化学技术检测各组动物肝组织Ⅰ、Ⅲ型胶原的表达。结果：芪参益气滴丸干预组与治疗组大鼠的肝纤维化程度、肝组织中Ⅰ型与Ⅲ型胶原mRNA水平及肝组织中Ⅰ型与Ⅲ型胶原的阳性表达，均分别较模型组与模型对照组显著减轻与下降。结论：芪参益气滴丸能明显减轻肝组织病理改变和肝纤维化程度．抑制Ⅰ、Ⅲ型胶原的表达是其抗肝纤维化的机制。     

成纤维细胞激活蛋白在肝纤维化模型大鼠肝组织中的动态表达

目的:观察大鼠肝纤维化形成过程中成纤维细胞激活蛋白(fibroblast activation protein, FAP)的动态表达变化特点。方法:Wistar雄性大鼠分为正常对照组和模型组。模型组ip 0.5%二甲基亚硝胺复制肝纤维化模型, 于造模1、2、3周分别收集肝组织标本, 造模4周后处死大鼠, 收集血清和肝组织标本。全自动生化仪测定丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)、总胆红素(TBIL)、谷氨酰转肽酶(GGT)和白蛋白(ALB), HE、天狼猩红染色观察病理形态, 试剂盒测定肝组织羟脯氨酸;real-time PCR和western blotting法检测肝组织FAP基因和蛋白表达。结果:模型组肝功能较正常组明显下降, 组织病理形态学和羟脯氨酸测定显示模型组肝损伤明显, 纤维化形成。real-time PCR和western blotting显示FAP基因和蛋白随造模时间延长表达逐渐增高。结论:FAP伴随大鼠肝纤维化模型形成逐渐增加, 与肝纤维化形成密切相关。     

Cytotoxicity and mutagenicity of dimethylnitrosamine in mammalian cells (CHO/HGPRT system): Enhancement by calcium phosphate

The cytotoxicity and mutagenicity of dimethylnitrosamine (DMN) was determined in the CHO/HGPRT system. Metabolic activation of the promutagen was achieved by use of a liver homogenate supernatant (S9) prepared from Aroclor 1254-induced Sprague-Dawley rats. The cytotoxic and mutagenic effects of DMN were enhanced by the inclusion of calcium chloride in the incubation mix, and this enhancement was dependent on the presence of sodium phosphate. Under conditions that yielded maximal activity (10 mM calcium chloride, 10 mM magnesium chloride, 50 mM sodium phosphate), an apparent calcium phospate precipitate was observed. DMN activity increased with increasing amounts of S9 protein over the range 0.3–3.0 mg/ml in the S9 mix and appeared to plateau at higher concentrations. The mutagenicity of DMN can be described as 110 mutants/10⁶ cells per mM DMN per mg/ml S9 protein per hour.     

A short-term test to detect organotropic specificity of carcinogens

Transplacental administration of 200 mg/kg of 3,4-benzpyrene (Bp) by intraperitoneal injection caused marked increase in 8-azaguanine (8AG)-resistant mutations in lung (75.210⁷ cells) and total body cells. Morphological transformations and chromosome aberrations were also observed in lung and total body cells. On transplacental administration of 200 200 mg/kg of dimethylnitrosamine (DMN), the highest rates of morphological transformation (6.53%) and 8AG-resistant mutation (12810⁷ cells) were induced in cells of liver origin, and chromosome abnormalities were also detected in liver and total body cells. Transplacental administration of 100 mg/kg of nitrosomethylurea (NMU) caused a marked increase in transformed colonies (4.08–4.40%) and 8AG-resistant mutations (134.8 and 79.910⁷ cells) of brain and total body cells. The cells from mice and rats that were most affected by transplacental administration of these chemicals were derived from the respective target organs of these chemicals in vivo.     

The effects of dimethylnitrosamine and allyl alcohol on primary maintenance cultures of adult rabbit hepatocytes

Cultures of adult rabbit hepatocytes have been used to study the early toxic effects of 2 model hepatotoxins, dimethylnitrosamine and allyl alcohol. Leakage of glutamate oxaloacetate transaminase and glutamate pyruvate transaminase into the cell culture medium was a sensitive indicator of plasma membrane damage by these compounds and a dose-response relationship was observed. By contrast, γ-glutamyltranspeptidase and alkaline phosphatase were insensitive markers. The effects of dimethylnitrosamine were slower to develop. Dimethylnitrosamine also produced a dose-related inhibition of protein synthesis after 4 h, a decrease in NADPH diaphorase and an increase in non-specific esterase after 20 h. Dimethylnitrosamine, unlike allyl alcohol, caused extensive disruption of ribosome association with the endoplasmic reticulum.     

Effect of dimethylnitrosamine on the induction of chromosomal aberrations in male mice and their F1 offspring

C₃H strain male mice were treated with dimethylnitrosamine (DMN) during 8 successive weeks at dose levels of 0.05 and 0.1 mg/kg per day: chromosomal translocations were not produced.     

Modification of lung tumor development in A/J mice

Strain A mice were injected with urethan, 3-methylcholanthrene or dimethylnitrosamine and given repeated injections of butylated hydroxytoluene (BHT). This treatment significantly increased multiplicity of lung tumors induced by all 3 carcinogens. Two other antioxidants, butylated hydroxyanisole (BHA) or α-tocopherol (vitamin E) did not enhance tumor formation, nor did methylcyclopentadienyl manganese tricarbonyl (MMT), an agen capable of producing cell proliferation in lung. Lungs were more susceptible to the carcinogenic action of urethan 2 weeks following BHT-induced injury, but not during the phase of acute cell proliferation in lung. It is concluded that the effects of BHT on lung tumor development in mice are not related to its properties as an antioxidant or to its capability to produce extensive cell proliferation in lung.