恩诺沙星在鲫鱼肝微粒体中的代谢及代谢关键酶的确定

抗生素因具有抗菌谱广、杀菌性强等特点使其被广泛应用于人类医药、畜牧业、农业和水产养殖业。其进入水生生物体内后，会在药物代谢酶的作用下发生代谢转化，产生生态毒性。本研究采用鲫鱼肝微粒体体外孵育法，探究恩诺沙星细胞色素P450酶作用下的代谢转化过程，并通过代谢抑制实验确定关键的代谢酶。实验结果表明，恩诺沙星体外代谢过程符合一级动力学方程，当恩诺沙星暴露浓度为1 mg·L-1时，其在肝微粒体中的消除速率常数k最大为0.00303 min-1，半衰期t1/2最短为228.8 min，应用HPLC-MS/MS技术，检测到了恩诺沙星脱乙基产物和羟基化产物；代谢抑制实验结果表明，CYP3A4在恩诺沙星代谢过程中起主要作用，是恩诺沙星代谢的关键酶。本研究结果为深入了解恩诺沙星在水生生物体内的代谢转化及其生态风险提供了基础数据。

Metabolism of Enrofloxacin in Liver Microsomes of Crucian Carp (Carassius ayratus) and its Key Enzymes in Vitro

Enrofloxacin are efficient and broad-spectrum which make it widely used in human medicine, animal husbandry, agriculture and aquaculture. Enrofloxacin can be metabolized by drug metabolizing enzymes in aquatic organisms, which will affect its ecological toxicity. In this study, the in vitro incubation method of liver microsomes was used to explore the metabolic transformation process of enrofloxacin under the action cytochrome P450 enzyme, and the key metabolic enzymes were determined by metabolic inhibition experiments. The results showed that the metabolic process of enrofloxacin in fish liver microsomes met the first-order kinetic equation, the maximum depuration rate constants (k) of enrofloxacin in the fish liver microsomes were 0.00303 min-1 and the minimum half-lives (t1/2) were 228.8 min in 1 mg·L-1 of enrofloxacin exposure concentrations. High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to identify the metabolites and metabolic pathways of enrofloxacin in liver microsomes. Two major metabolites were found, including the product of deethylation and hydroxylation. Further, this metabolic inhibition study showed that cytochrome P3A4 might be the key enzyme involved in the metabolism of enrofloxacin. Overall, this study provides basic data for further understanding of the biotransformation and ecological risk of enrofloxacin in aquatic organisms.