Kleeberg U, Klinger W
Acta Biol Med Ger. 1982;41(7-8):675-87.
Dimethylnitrosamine (DMN)-N-demethylation by 10,000 x g liver supernatant follows a typical Michaelis-Menten kinetics with one apparent Km (4.0 . 10(-4) M) and V max (0.460 nmole/mg . min) of 30-day-old male rats. The investigation of hepatic DMN-N-demethylation in dependence on age reveals maximum activities in 30- to 60-day-old male rats. The demethylating enzyme activity is inducible by phenobarbital (PB), not by 3-methylcholanthrene (3-MC). Pretreatment of animals with PB plus 3-MC resulted in reduced inducibility compared with PB-pretreatment alone. Probably this is not due to an inhibition of PB-induction by 3-MC, but effected by PB residues in the liver tissue and in the incubation mixture. The elimination rate of PB in young rats seems to be retarded if high doses of the inducers PB and 3-MC are administered simultaneously. Additionally changes in inducible cytochrome P-450 subspecies have to be considered.
10000×g 肝匀浆上清液对二甲基亚硝胺（DMN）的 N-去甲基化反应遵循典型的米氏动力学，30 日龄雄性大鼠的表观 Km 为 4.0×10⁻⁴ M，Vmax 为 0.460 纳摩尔/毫克·分钟。对不同年龄大鼠肝脏 DMN-N-去甲基化的研究表明，30 至 60 日龄雄性大鼠的酶活性最高。去甲基化酶活性可被苯巴比妥（PB）诱导，但不能被 3-甲基胆蒽（3-MC）诱导。与单独用 PB 预处理相比，用 PB 加 3-MC 预处理动物会导致诱导性降低。这可能不是由于 3-MC 抑制了 PB 的诱导作用，而是受肝脏组织和孵育混合物中 PB 残留的影响。如果同时给予高剂量的诱导剂 PB 和 3-MC，幼鼠体内 PB 的消除速率似乎会减慢。此外，还必须考虑可诱导细胞色素 P-450 亚型的变化。
