Catechol metabolites of zeranol and 17尾-estradiol: A comparative in vitro study on the induction of oxidative DNA damage and methylation by catechol-O-methyltransferase
- 作者：Stefanie C. Fleck ; Andreas A. Hildebrand ; Erika Pfeiffer ; Manfred Metzler ; Manfred.Metzler@kit.edu
- 关键词：amu ; atomic mass units ; COMT ; catechol-O-methyltransferase ; CYP ; cytochrome P450 ; DAD ; diode array detector ; DMSO ; dimethylsulfoxide ; E1 ; estrone ; E2 ; 17尾-estradiol ; ESI ; electrospray ionization ; HO ; hydroxy ; IBX ; ortho-iodoxybenzoic acid ; LC ; liquid chr
- 刊名：Toxicology Letters
- 出版年：2012
- 期刊代码：49_03784274
- 类别：pha
- 出版时间：5 April, 2012
- 卷：210
- 期：1
- 页码：9-14
- 文件大小：346 K
摘要
伪-Zearalanol (伪-ZAL, zeranol) is a highly estrogenic macrocyclic 尾-resorcylic acid lactone, which is used as a growth promotor for cattle in various countries. We have recently reported that 伪-ZAL and its major metabolite zearalanone (ZAN) are hydroxylated at the aromatic ring by microsomes from human liver in vitro, thereby forming two catechol metabolites each. Thus, the oxidative metabolism of 伪-ZAL and ZAN resembles that of the endogenous steroidal estrogens 17尾-estradiol (E2) and estrone (E1), which also give rise to two catechols each. As these catechol metabolites are believed to mediate the carcinogenicity of E2 and E1 by causing oxidative DNA damage and DNA adducts, their methylation by catechol-O-methyltransferase (COMT) is an important inactivation pathway. Here we report that hepatic microsomes from five species generate catechol metabolites of 伪-ZAL and ZAN, the highest amounts being formed by human liver microsomes, followed by rat, mouse, steer and swine. The microsomal extracts and the individual catechols of 伪-ZAL, ZAN, E2 and E1 were found to induce oxidative DNA damage, as measured by the formation of 8-oxo-7,8-dihydro-2鈥?deoxyguanosine in a cell-free system. The ranking of pro-oxidant activity was 15-HO-ZAN > 15-HO-伪-ZAL 鈮?#xA0;4-HO-E2/E1 鈮?#xA0;2-HO-E2/E1 > 13-HO-ZAN > 13-HO-伪-ZAL. With respect to the rate of methylation by human hepatic COMT, the ranking was 2-HO-E2/E1 >> 4-HO-E2/E1 > 15-HO-伪-ZAL/ZAN >> 13-HO-伪-ZAL/ZAN. Thus, some catechol metabolites of 伪-ZAL and ZAN are better pro-oxidants and poorer substrates of COMT than the catechols of E2 and E1. These findings warrant further investigations into the genotoxic potential of 伪-ZAL, which may constitute another biological activity in addition to its well-known estrogenicity.