In vitro metabolism and inductive or inhibitive effect of DL111 on rat cytochrome P4501A enzyme

Abstract

In vitro metabolism and the inductive or inhibitive effect of DL111, a non-hormonal early pregnancy-terminating agent, toward cytochrome P450 (CYP) enzymes in rat liver microsomes were studied. In vitro metabolism of DL111 was performed in different rat liver microsomes (pretreated with phenobarbital (PB), dexamethasone (Dex), β-naphthoflavone (BNF), DL111, respectively) and the catalytic abilities of these microsomes for DL111 were compared with control group. DL111 was well metabolized in microsomes pretreated with β-naphthoflavone and itself. The K m and V max was 41.76±3.26 μM and 15.34±1.03 nmol min −1 mg −1 protein for β-naphthoflavone group, 48.17±6.06 μM and 17.54±1.79 nmol min −1 mg −1 protein for DL111 group, 77.81±4.73 μM and 3.087±0.202 nmol min −1 mg −1 protein for control group, respectively. The rats were pretreated intraperitoneally with the same daily dose of DL111 for different days. The DL111-pretreated microsomal enzymatic activities were evaluated by measuring the metabolic abilities for specific substrates of various enzymes. The results showed that DL111 had the same inductive function as β-naphthoflavone (the specific inducer of CYP1A) toward rat liver microsomes. The inhibitive effect of DL111 on CYP1A was investigated by coincubating DL111 with the specific substrates of CYP1A—ethoxyresorufin or phenacetin in the microsome induced by β-naphthoflavone, and the inhibitive level was compared with fluvoxamine (Flu), the specific inhibitor of CYP1A. DL111 inhibited significantly the metabolism of phenacetin and ethoxyresorufin with the inhibition constant ( K i) 6.836±0.10 and 1.222±0.230 μM, respectively and its inhibition potential on CYP1A was higher than fluvoxamine.