Contribution of CYP1A2 in the hepatic metabolism of melatonin: studies with isolated microsomal preparations and liver slices
Contribution of CYP1A2 in the hepatic metabolism of melatonin: studies with isolated microsomal preparations and liver slices
复制标题
CYP1A2 在褪黑激素肝脏代谢中的贡献：分离微粒体制剂和肝切片的研究
DOI：
--
复制
发表时间：
2001
影响因子：
10.3
通讯作者：
C. Ioannides
中科院分区：
文献类型：
--
作者：
D. Skene;E. Papagiannidou;E. Hashemi;Jacquie Snelling;D. Lewis;M. Fernández;C. Ioannides
本研究的目的是通过监测大鼠肝脏线粒体后制备物和精密切割肝脏切片中6-硫酸氧褪黑激素的水平，确定催化褪黑激素6-羟基化的酶系统。褪黑激素6-羟化酶活性位于微粒体中，并由NADPH支持，但不是NADH。用β-萘甲酮处理大鼠，使褪黑激素形成的6-硫酸酯氧基褪黑激素增加了两倍多，但仅使6-羟基褪黑激素的硫酸酯结合适度增加（25%）。当褪黑激素或6-羟基褪黑激素作为底物时，用苯巴比妥、丙酮、地塞米松和氯贝特处理大鼠不会增加6-硫酸氧褪黑激素的产生。在研究的许多细胞色素P450抑制剂中，只有呋拉茶碱显著抑制褪黑激素转化为6-sulphatoxy褪黑激素，而对6-羟基褪黑激素的磺基缀合没有任何伴随作用。当肝切片与褪黑激素一起孵育时，用β-萘啶酮和较小程度的苯巴比妥处理大鼠，升高了培养基中6-硫酸氧褪黑激素的水平。当β-萘啶酮处理的大鼠的切片与6-羟基褪黑激素孵育时，没有观察到这种增加，而苯巴比妥处理的大鼠的切片观察到适度增加。用丙酮、地塞米松或氯贝丁酯处理大鼠未能调节由褪黑激素或6-羟基褪黑激素产生的6-硫酸氧褪黑激素的水平。分子建模分析显示，褪黑激素具有高面积/深度比2，显示出CYP 1A 2底物的特征，并且可以容易地容纳在有利于6-羟基化的位置的人CYP 1A 2活性位点中。总之，所有上述数据提供了强有力的实验证据，证明CYP 1A 2是褪黑激素6-羟基化的重要催化剂。
The objective of the present studies was to define the enzyme systems catalysing the 6‐hydroxylation of melatonin, by monitoring the levels of 6‐sulphatoxymelatonin in rat hepatic postmitochondrial preparations and in precision‐cut liver slices. Melatonin 6‐hydroxylase activity was localized in microsomes and was supported by NADPH, but not NADH. Treatment of rats with β‐naphthoflavone more than tripled 6‐sulphatoxymelatonin formation from melatonin, but gave rise only to a moderate increase (25%) in the sulphate conjugation of 6‐hydroxymelatonin. Treatment of rats with phenobarbitone, acetone, dexamethasone and clofibrate did not increase 6‐sulphatoxymelatonin generation when either melatonin or 6‐hydroxymelatonin served as substrates. Of a number of cytochrome P450 inhibitors investigated, only furafylline inhibited markedly the conversion of melatonin to 6‐sulphatoxymelatonin without any concomitant effect on the sulphoconjugation of 6‐hydroxymelatonin. When liver slices were incubated with melatonin, treatment of rats with β‐naphthoflavone, and to a lesser extent phenobarbitone, elevated the levels of 6‐sulphatoxymelatonin in the culture medium. No such increase was seen when slices from β‐naphthoflavone‐treated rats were incubated with 6‐hydroxymelatonin, whereas a modest increase was seen with slices from phenobarbitone‐treated rats. Treatment of rats with acetone, dexamethasone or clofibrate failed to modulate the levels of 6‐sulphatoxymelatonin generated from either melatonin or 6‐hydroxymelatonin. Molecular modelling analysis revealed that melatonin had a high area/depth2 ratio, displayed characteristics of CYP1A2 substrates and could be readily accommodated into the human CYP1A2 active site in a position favouring 6‐hydroxylation. Collectively, all the above data provide strong experimental evidence that CYP1A2 is an important catalyst of the 6‐hydroxylation of melatonin.
大鼠体内和体外 1-甲基黄嘌呤代谢。
DOI：
--
发表时间：
1987
期刊：
Drug metabolism and disposition: the biological fate of chemicals
影响因子：
--
作者：
Reinke,LA;Nakamura,M;Logan,L;Christensen,HD;Carney,JM
通讯作者：
Carney,JM