Pham-Huy C, Sadeg N, Becue T, Martin C, Mahuzier G, Warnet J M, Hamon M, Claude J R
Laboratoire de Toxicologie (EA 207), Faculté de Pharmacie, Université René-Descartes, Paris, France.
Arch Toxicol. 1995;69(5):346-9. doi: 10.1007/s002040050182.
Cyclosporin A (CsA) is in vivo mainly metabolized by hepatic cytochrome P450 IIIA to more than 21 metabolites, the major ones known as: M1, M17 and M21. The aim of this work is to explore the in vitro metabolism of CsA after incubation, in the presence of NADPH, with renal or hepatic microsomes obtained from rabbits pretreated with rifampycin (enzyme inducer) or erythromycin (enzyme inhibitor). The presumed metabolites were separated by semi-preparative high-performance liquid chromatography (HPLC) and identified in each collected fraction by fluorescence polarization immunoassay (FPIA) (HPLC-FPIA) using a non-specific polyclonal antibody. They were also analyzed by HPLC-mass spectrometry (MS) using fast atom bombardment (HPLC-MS-FAB). Five collected fractions gave positive results with FPIA. The major metabolites found were M1, M17 and M21 after identification by HPLC-MS-FAB and comparison with three corresponding standard metabolites. The CsA biotransformation rates were calculated by the amount of unmetabolized CsA and were linear with time. These mean rates (Vm) for 12-min incubation by renal microsomes of rabbits treated with rifampicin or erythromycin or untreated (control) were 0.11, 0.02 and 0.04 nmol/min x mg microsomal protein, respectively. These rates were 15-, 37-, and 30-fold lower than those obtained with hepatic microsomes of rabbits treated identically. As CsA metabolites are less cytotoxic than the parent drug, this weak renal biotransformation of CsA after in vitro incubation should be one of the mechanisms of its in vivo nephrotoxicity.
环孢素A（CsA）在体内主要由肝细胞色素P450 IIIA代谢为21种以上的代谢产物，其中主要的代谢产物有：M1、M17和M21。本研究的目的是探讨在存在NADPH的情况下，环孢素A与从用利福平（酶诱导剂）或红霉素（酶抑制剂）预处理的兔子获得的肾或肝微粒体孵育后的体外代谢情况。假定的代谢产物通过半制备高效液相色谱（HPLC）分离，并使用非特异性多克隆抗体通过荧光偏振免疫测定（FPIA）（HPLC-FPIA）在每个收集的馏分中进行鉴定。它们还通过使用快原子轰击的HPLC-质谱（MS）进行分析（HPLC-MS-FAB）。五个收集的馏分用FPIA给出了阳性结果。通过HPLC-MS-FAB鉴定并与三种相应的标准代谢产物比较后，发现的主要代谢产物是M1、M17和M21。环孢素A的生物转化速率通过未代谢的环孢素A的量计算，并且与时间呈线性关系。用利福平或红霉素处理或未处理（对照）的兔子的肾微粒体在12分钟孵育时的这些平均速率（Vm）分别为0.11、0.02和0.04 nmol/分钟×毫克微粒体蛋白。这些速率比用相同处理的兔子的肝微粒体获得的速率分别低15倍、37倍和30倍。由于环孢素A的代谢产物比母体药物的细胞毒性小，体外孵育后环孢素A这种微弱的肾生物转化应该是其体内肾毒性的机制之一。
