细菌与内源性N-亚硝酰胺合成的研究

STUDIES ON BACTERIALLY MEDIATED AND ENDOGENOUS N-NITROSAMIDE SYNTHESIS

目的：许多研究证实，萎缩性胃炎患者胃内细菌繁殖增多与Ｎ－亚硝酰胺含量升高有关。因此该实验模拟胃低酸情况下，胃内细菌催化Ｎ－亚硝酰胺合成情况及合成量为研究宗旨。方法：采用患者空腹胃液中经培养、分离、鉴定的１３种４６株细菌，以甲基脲（ＭＵ）及亚硝酸纳（ＮａＮＯ２）为底物加入活菌悬液在近中性条件下进行Ｎ－甲基－Ｎ－亚硝基脲（ＭＮＵ）催化合成反应，用ＨＰＬＣ－ＰＨＰＳ－ＴＥＡ法定量测定。结果：（ａ）ｐＨ分别为５，６，７时，１３株细菌催化ＭＮＵ合成能力以ｐＨ６时最高，占９２３％。（ｂ）ｐＨ６时，４６株细菌催化ＭＮＵ合成能力不同；经筛选阳性菌６株，其中金黄色葡萄球菌合成量最高。（ｃ）多株菌混合液催化实验，催化能力与混合菌中阳性菌个体所占比例有关，比例高合成能力强；阳性菌与阴性菌相混合不影响其催化合成能力。结论：胃内细菌具有催化强致癌物Ｎ－亚硝酰胺合成的能力，其合成量决定于胃液ｐＨ、阳性菌株浓度。

Objective:The experimental purpose is to find out that bacteria isolated from gastric juice with chronic gastritis could catalyze formation of N-nitrosamide (NAD) in the simulated stomach condition. Methods:46 strains of 13 species bacteria were isolated respectively for gastric juice with chronic gastroduodenal disorders in the high risk area for gastric carcinoma. MU and NaNO2 was catalyzed by the suspensive solution of bacteria in neutral pH. A selective HPLC-PHPS-TEA method to separate and detect standard N-methyl-N-nitrosourea(MNU) was established. Results:a.The catalyzing nitrosative ability was the highest(923%) at pH6 point among 13 strains bacteria in neutral pH 5～7. b.6 out of 46 strains positive bacteria with catalyze formation of MNU in the simulated gastric juice (pH6). 2 strains of S.aureus catalyzing nitrosative ability is the highest. c.The experiment were showed ability of catalyzed relate to proportion of positive amount in mixed bacteria, and the more higher ratio the more higher ability to synthesize. The ability of positive bacteria with catalyzed formation of MNU had not infected each other in mixed juice. Conclusion:The study show that bacteria could catalyze the endogenous formation of nitrosamide and the synthetic measure decided by pH,consistency of positive bacteria and precursors of material.