Oda Y, Imaoka S, Nakahira Y, Asada A, Fujimori M, Fujita S, Funae Y
Department of Anesthesiology and Intensive Care Medicine, Osaka City University Medical School, Japan.
Biochem Pharmacol. 1989 Dec 15;38(24):4439-44. doi: 10.1016/0006-2952(89)90654-0.
The metabolism of lidocaine was studied using rat liver microsomes or a reconstituted lidocaine monooxygenase system with one of eight forms of cytochrome P-450 purified from liver microsomes from untreated- (P450 UT-2 and UT-5), phenobarbital- (P450 PB-1, PB-2, PB-4, and PB-5) or 3-methylcholanthrene- (P450 MC-1 and MC-5) treated rats. A reverse phase high-performance liquid chromatography system capable of simultaneously assaying four major lidocaine metabolites, namely, monoethylglycinexylidide (MEGX), 3-hydroxylidocaine (3-OH LID), methylhydroxylidocaine (Me-OH LID) and glycinexylidide (GX), was employed to determine the rate of formation of each metabolite. Untreated microsomes generated MEGX, Me-OH LID, and 3-OH LID, but the formation of GX was not detected. In male rat liver microsomes, MEGX was the major metabolite of lidocaine when a concentration of 1 mM was employed. The formation of MEGX and Me-OH LID was increased significantly (P less than 0.01) by microsomes from phenobarbital-treated rats, and the formation of 3-OH LID was increased with 3-methylcholanthrene. The study with the reconstituted system with purified cytochrome P-450 isozymes revealed that all eight forms of cytochrome P-450 used have an ability to N-deethylate lidocaine to form MEGX. Among these isozymes, cytochrome P450 PB-4 and P450 UT-2 showed a higher turnover number for the formation of MEGX. Me-OH LID was formed exclusively by P450 PB-5, and 3-OH LID exclusively by P450 MC-1. Selectivity of cytochrome P450 PB-5 for aromatic methyl hydroxylation of lidocaine was confirmed by an inhibition study; formation of Me-OH LID by microsomes of rats treated with phenobarbital was inhibited completely by antibody against P450 PB-5. It was concluded that different cytochrome P-450 isozymes metabolize lidocaine with a different rate and different position selectivities. Since a specific substrate of cytochrome P450 PB-5 (P-450e) is not known, lidocaine may be a useful substrate for the identification of P450 PB-5.
利用大鼠肝微粒体或重组利多卡因单加氧酶系统，研究了利多卡因的代谢情况。该重组系统含有从未经处理（P450 UT - 2和UT - 5）、苯巴比妥处理（P450 PB - 1、PB - 2、PB - 4和PB - 5）或3 - 甲基胆蒽处理（P450 MC - 1和MC - 5）的大鼠肝微粒体中纯化得到的8种细胞色素P - 450形式之一。采用一种能够同时测定4种主要利多卡因代谢物，即单乙基甘氨酰二甲苯酰胺（MEGX）、3 - 羟基利多卡因（3 - OH LID）、甲基羟基利多卡因（Me - OH LID）和甘氨酰二甲苯酰胺（GX）的反相高效液相色谱系统，来测定每种代谢物的生成速率。未经处理的微粒体可生成MEGX、Me - OH LID和3 - OH LID，但未检测到GX的生成。在雄性大鼠肝微粒体中，当使用1 mM浓度的利多卡因时，MEGX是主要代谢物。苯巴比妥处理的大鼠的微粒体使MEGX和Me - OH LID的生成显著增加（P小于0.01），3 - 甲基胆蒽使3 - OH LID的生成增加。对含有纯化的细胞色素P - 450同工酶的重组系统的研究表明，所使用的8种细胞色素P - 450形式都有将利多卡因N - 去乙基化形成MEGX的能力。在这些同工酶中，细胞色素P450 PB - 4和P450 UT - 2在MEGX生成方面表现出较高的转换数。Me - OH LID仅由P450 PB - 5生成，3 - OH LID仅由P450 MC - 1生成。通过抑制研究证实了细胞色素P450 PB - 5对利多卡因芳香甲基羟基化的选择性；用苯巴比妥处理的大鼠的微粒体生成Me - OH LID的过程被抗P450 PB - 5抗体完全抑制。得出的结论是，不同的细胞色素P - 450同工酶以不同的速率和不同的位置选择性代谢利多卡因。由于细胞色素P450 PB - 5（P - 450e）的特异性底物尚不清楚，利多卡因可能是用于鉴定P450 PB - 5的有用底物。
