Chen L, Lee M, Hong J Y, Huang W, Wang E, Yang C S
Laboratory for Cancer Research, College of Pharmacy, Rutgers University, Piscataway, NJ 08855-0789.
Biochem Pharmacol. 1994 Dec 16;48(12):2199-205. doi: 10.1016/0006-2952(94)00435-8.
Previous studies have demonstrated that cytochrome P450 2E1 (P450 2E1) catalyzes the oxidation of acetone in vitro. The present study was designed to determine the importance of P450 2E1 in the catabolism of acetone in rats using diallyl sulfide (DAS) as an inhibitor of this enzyme. After a single intragastric dose of DAS, blood samples were collected from rats at different time points, and blood acetone concentrations were measured by gas chromatography. In a low DAS dose (50 mg/kg body weight) group, the maximum acetone level of 6-fold higher than the normal level was reached at 6 hr; the acetone level returned to normal at 48 hr. In a high dose (200 mg/kg) group, the maximum acetone level of 9-fold higher than the normal level was reached at 12 hr; the acetone level returned to normal at 60 hr. The turnover time and fractional turnover rate of elevated acetone were 15.8 +/- 0.5 hr and 0.054 +/- 0.001 hr-1, respectively, for the low dose, and 19.2 +/- 0.6 hr and 0.046 +/- 0.005 hr-1, respectively, for the high dose. In a chronic experiment, DAS (50 and 200 mg/kg, i.g.) was given to rats daily for 29 days, and elevated blood acetone levels were observed during the entire experimental period: 2.0 to 2.8 micrograms/mL for the low dose and 3.4 to 3.9 micrograms/mL for the high dose at 24 hr after the 1st, 7th, 14th and 28th doses versus 0.8 to 0.9 micrograms/mL for the control. The increase of blood acetone level was closely related to the decreases of N-nitrosodimethylamine (NDMA) demethylase activity and P450 2E1 content in liver microsomes. Consistent with the lack of cumulative effect from the multiple doses of DAS on acetone level, rather stable levels of the DAS metabolites, diallyl sulfoxide (45.0 micrograms/mL, range: 33.8 to 58.6 micrograms/mL) and diallyl sulfone (11.7 micrograms/mL, range: 6.9 to 15.6 micrograms/mL), were observed at 24 hr after the 1st, 7th, 21st and 28th doses with DAS (200 mg/kg) in the chronic experiment. It is likely that the inactivation and inhibition of P450 2E1 by DAS and its metabolites block the oxidation of acetone and cause its elevation in blood. The results strongly suggest an important role of P450 2E1 in acetone catabolism under physiological conditions.
先前的研究表明，细胞色素P450 2E1（P450 2E1）在体外催化丙酮的氧化。本研究旨在使用二烯丙基硫醚（DAS）作为该酶的抑制剂，确定P450 2E1在大鼠丙酮分解代谢中的重要性。单次灌胃给予DAS后，在不同时间点采集大鼠血样，采用气相色谱法测定血丙酮浓度。在低剂量DAS（50mg/kg体重）组中，6小时时丙酮水平达到比正常水平高6倍的最大值；48小时时丙酮水平恢复正常。在高剂量（200mg/kg）组中，12小时时丙酮水平达到比正常水平高9倍的最大值；60小时时丙酮水平恢复正常。低剂量组中，升高的丙酮的周转时间和分数周转率分别为15.8±0.5小时和0.054±0.001小时-1，高剂量组分别为19.2±0.6小时和0.046±0.005小时-1。在一项慢性实验中，每天给大鼠灌胃DAS（50和200mg/kg），持续29天，在整个实验期间观察到血丙酮水平升高：在第1、7、14和28次给药后24小时，低剂量组为2.0至2.8μg/mL，高剂量组为3.4至3.9μg/mL，而对照组为0.8至0.9μg/mL。血丙酮水平的升高与肝微粒体中N-亚硝基二甲胺（NDMA）脱甲基酶活性和P450 2E1含量的降低密切相关。与多次给药DAS对丙酮水平无累积效应一致，在慢性实验中，给予DAS（200mg/kg）后，在第1、7、21和28次给药后24小时观察到DAS代谢产物二烯丙基亚砜（45.0μg/mL，范围：33.8至58.6μg/mL）和二烯丙基砜（11.7μg/mL，范围：6.9至15.6μg/mL）的水平相当稳定。DAS及其代谢产物可能使P450 2E1失活并抑制其活性，从而阻断丙酮的氧化并导致其血中水平升高。结果强烈表明P450 2E1在生理条件下的丙酮分解代谢中起重要作用。
