代谢
单烯霉素是一种在兽医实践中广泛用作球虫抑制剂和生长促进剂的离子载体抗生素。本研究探讨了单烯霉素在大鼠、马、猪、肉鸡和牛的肝微粒体中的氧化代谢。通过测量释放的甲醛量,发现单烯霉素O-脱甲基化速率在所有物种中几乎相同,但总单烯霉素代谢(通过高效液相色谱法测量底物消失速率来估计)在牛中最高,在大鼠、肉鸡和猪中为中等,在马中最低。当以转化数(每分钟每纳米摩尔细胞色素P450-1代谢的单烯霉素纳米摩尔数)表示时,催化效率(肉鸡>牛>猪≈大鼠>马)与物种对这种离子载体毒副作用易感性的已知差异呈负相关,这种差异表现为马的口服LD50为2-3 mg/kg体重,牛为50-80 mg/kg体重,肉鸡为200 mg/kg体重。肉鸡和牛的微粒体还显示出对两种P450 3A依赖性底物(红霉素和三乙酰奥兰多霉素)的催化效率最高,以及与大鼠P450 3A1/2抗体的免疫检测蛋白交叉反应水平最高。
The oxidative metabolism of monensin, an ionophore antibiotic extensively used in veterinary practice as a coccidiostat and a growth promoter, was studied in hepatic microsomal preparations from horses, pigs, broiler chicks, cattle and rats. As assayed by the measurement of the amount of the released formaldehyde, the rate of monensin O-demethylation was nearly of the same order of magnitude in all species, but total monensin metabolism, which was estimated by measuring the rate of substrate disappearance by a high-performance liquid chromatography (HPLC) method, was highest in cattle, intermediate in rats, chicks and pigs, and lowest in horses. When expressed as turnover number (nmol of metabolized monensin/min nmol cytochrome P450-1), the catalytic efficiency (chick >> cattle >> pig approximately rat > horse) was found to correlate inversely with the well known interspecies differences in the susceptibility to the toxic effects of the ionophore, which is characterized by an oral LD50 of 2-3 mg/kg bodyweight (bw) in horses, 50-80 mg/kg bw in cattle and 200 mg/kg bw in chicks. Chick and cattle microsomes also displayed both the highest catalytic efficiency toward two P450 3A dependent substrates (erythromycin and triacetyloleandomycin) and the highest immunodetectable levels of proteins cross-reacting with anti rat P450 3A1/2. ...
来源:Hazardous Substances Data Bank (HSDB)