饮茶对香烟中特异性亚硝胺－NNK诱发小鼠肺癌基因表达的影响

通过研究饮茶对香烟中特异性亚硝胺－ＮＮＫ诱发小鼠肺癌基因表达的影响，对饮茶可拮抗香烟致癌作用的结果做进一步验证，并对其作用机理进行探讨。所使用方法为国内外尚属新的技术，即非同位素标记探针测定基因表达。其结果表明阳性小鼠给ＮＮＫ４周后，ｃ－ｍｙｃ和ｃ－ｒａｆ基因表达水平明显增高，而小鼠若同时饮绿茶则可抑制这种增高，抑制率达５０％和２０％，到第８周时阳性对照组的ｃ－ｍｙｃ和ｃ－ｒａｆ基因水平恢复正常。与此相对应，ｃ－Ｈ－ｒａｓ基因在第８周时表达增高，约为阴性组３倍，饮茶对此同样有抑制作用，抑制率为５０％。在第２、４和８周均未见阳性对照组ｖｓｉｓ基因表达水平的改变。

Effect of drinking tea on the tobacco-specific nitrosamine-NNK induced lung oncogene expression in mouse

The study was designed to study the effects of drinking tea on the tobacco-specific nitrosamine──4-(methynitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induced mouse lung oncogene expression for the purpose of confirming the preventive effects of drink ing tea against tobacco smoking and illustrating the mechanisms of drinking tea in cancer prevention. The nonradioactive slot-blot analysis method was used to determine oncogene expression. The results indicate that 4 weeks after NNK administration (i.p.),the expression of c-myc and c-raf in the positive control mice was significantly increased. However, when drinking water was replaced by drinking green tea, the expression of these two oncogenes was reduced to 50% and 20% respectively, as compared with the positive control group. After 8 weeks,the expression of c-myc and c-raf of the positive control mice returned to normal; but at the same time, the expression of c-H-ras increased to three times as that in the negative control mice. Again,the tea drinking mice showed an 50% inhibition in cH-ras expression. No increase was observed in v-sis gene expression in the positive control mice at 2, 4 or 8 weeks after NNK administration.