应用现代酶学实验方法观察了鼠肝微粒体药物代谢酶的3项指标随时间变化的情况，结果表明：细胞色素P450总量、NADPH细胞色素C还原酶和二甲基亚硝胶脱甲基酶3项指标均具昼夜节律性变化。这一结果对探讨中医学择时用药原则有一定意义。择时用药即选择药物最佳作用时间，从而达到临床效果的时间治疗学方法。

Diurnal rhythmic activities of three liver microsomal drug metabolizing enzymes,cytochrome P450,NVADPH-cytochrome C reductase and N-nitrosodimethyl amine demethylase were selected and studies.All of them had a remarkable diurnal rhythm in rats.Their peak values were from 9:00 PM to 12:00 PM midnight,while the valley were at 6:00 dawn.Such rhythmicity correlated well with the metabolism of most TCM.Thus it was postulated that an optimum time for TCM administration could be selected based on this princi-ple.