Pharmacokinetics of metyrapone and metyrapol enantiomers was studied in the rat to determine the stereoselective reductive metabolism of metyrapone. The HPLC method using a chiral column was developed for the stereoselective analysis of metyrapol enantiomers in rat plasma. The AUC ratio of (-)- and (+)-metyrapol appeared in rat plasma after i.v. administration of metyrapone was about 3 : 1. The interconversion of (-)- or (+)-metyrapol to its antipode was negligible, and the reverse reaction from metyrapol to metyrapone was insignificant. There were similar kinetic parameters of (-)-metyrapol to those of (+)-metyrapol after i.v. administration of racemic metyrapol. These results indicate metyrapone displays product-stereoselective reductive metabolism in the rat. The inhibition of steroid 11β-hydroxylase by metyrapone, racemic metyrapol, (-)-metyrapol or (+)-metyrapol was analyzed in rat adrenal homogenates. Metyrapol was equally as potent as metyrapone in the inhibition of steroid 11β-hydroxylase and each enantiomer of metyrapol showed similar inhibitory activity on the rat adrenal steroid 11β-hydroxylase. These results indicate there is an insignificant difference in the inhibitory effects on steroid 11β-hydroxylase of metyrapol enantiomers, and that the inhibitory effects of metyrapol may be involved in the pharmacological activity of metyrapone in vivo.
研究了大鼠体内
甲孕酮和
甲孕酮对映体的药代动力学,以确定
甲孕酮的立体选择性还原代谢。采用手性色谱柱开发了高效
液相色谱法,用于大鼠血浆中
甲萘醌对映体的立体选择性分析。大鼠静脉注射
甲萘醌后,血浆中(-)-和(+)-甲
萘酚的AUC比约为3:1。(-)-或(+)-metyrapol与它的反式之间的相互转化可以忽略不计,而从metyrapol到metyrapone的逆反应也不明显。静脉注射外消旋
安乃近后,(-)-
安乃近与(+)-
安乃近的动力学参数相似。这些结果表明,甲基
吡咯酮在大鼠体内具有产物严格选择性还原代谢作用。在大鼠肾上腺匀浆中分析了甲
硫酮、外消旋
甲硫醇、(-)-
甲硫醇或(+)-
甲硫醇对类
固醇 11β- 羟化酶的抑制作用。在抑制类
固醇 11β- 羟化酶方面,Metyrapol 与 metyrapone 具有相同的效力,而且 metyrapol 的每种对映体对大鼠肾上腺类
固醇 11β- 羟化酶具有相似的抑制活性。这些结果表明,metyrapol对映体对
甾体11β-羟化酶的抑制作用差异不大,metyrapol的抑制作用可能参与了metyrapone在体内的药理活性。