Metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in mouse lung microsomes and its inhibition by isothiocyanates.

阅读量:

52

作者:

TJ SmithZY GuoPE ThomasFL ChungMA MorseK ElkindCS Yang

展开

摘要:

The tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induces lung tumors in rats, mice, and hamsters, and metabolic activation is required for the carcinogenicity. 2-Phenethyl isothiocyanate (PEITC), whose precursor gluconasturtiin (a glucosinolate) occurs in cruciferous vegetables, has been found to inhibit carcinogenesis by NNK. The purpose of the study was to investigate the enzymes involved in the metabolism of NNK in lung microsomes and to elucidate the mechanisms of inhibition of NNK metabolism by isothiocyanates. NNK metabolism in lung microsomes (isolated from female A/J mice) resulted in the formation of formaldehyde, 4-hydroxy-1-(3-pyridyl)-1-butanone (keto alcohol), 4-oxo-4-(3-pyridyl)butyric acid (keto acid), 4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone, and 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanol, displaying apparent Km values of 5.6, 5.6, 9.2, 4.7, and 2540 microM, respectively. Higher Km values in the formation of formaldehyde and keto alcohol were also observed. When cytochrome P-450 inhibitors [2-(diethylamino)ethyl 2,2-diphenylpentenoate] hydrochloride (100 microM), carbon monoxide (90%), and 9-hydroxyellipticine (10 microM) were used, NNK metabolism was inhibited by each 70, 100, and 30%, respectively. Methimazole (1 mM), an inhibitor of the flavin-dependent monooxygenase, inhibited the formation of 4-(methyl-nitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol by 20%, but had no effect on the formation of keto alcohol. Inhibitory antibodies against cytochromes P-450IIB1 and -2, P-450IA1, and P-450IA2 inhibited the formation of keto alcohol by 25, 15, and 0%, respectively. Administration of PEITC at doses of 5 and 25 mumol/mouse 2 h before sacrifice produced a 40 and 70% decrease in microsomal NNK metabolism, respectively. PEITC and 3-phenylpropyl isothiocyanate exhibited a mixed type of inhibition, and the competitive component of inhibition had apparent Ki values of 90 and 30 nM, respectively. Preincubation of PEITC in the presence of a NADPH-generating system did not result in a further decrease in the formation of NNK metabolites, indicating that the metabolism of PEITC was not required for the inhibition. When a series of isothiocyanates with varying alkyl chain length (phenyl isothiocyanate, benzyl isothiocyanate, PEITC, 3-phenylpropyl isothiocyanate, and 4-phenylbutyl isothiocyanate) were used, the potency of the inhibition increased with the increase in chain length.TRUNCATED AT 400 WORDS)

展开

DOI:

10.1007/BF01771458

被引量:

243

年份:

1990

通过文献互助平台发起求助,成功后即可免费获取论文全文。

相似文献

参考文献

引证文献

辅助模式

0

引用

文献可以批量引用啦~
欢迎点我试用!

关于我们

百度学术集成海量学术资源,融合人工智能、深度学习、大数据分析等技术,为科研工作者提供全面快捷的学术服务。在这里我们保持学习的态度,不忘初心,砥砺前行。
了解更多>>

友情链接

百度云百度翻译

联系我们

合作与服务

期刊合作 图书馆合作 下载产品手册

©2025 Baidu 百度学术声明 使用百度前必读

引用