Effects Of Kuianchun On Hepatic Cytochrome P450 Enzymes In Rats

Kuianchun, a structural derivative from quinoxaline 1,4-dioxide, is a new antibacterial and additive for animal which was developed by Lanzhou Institute of Animal Science and Veterinary Pharmaceutics of Chinese Academy of Agricultural Science. The previous study showed that it was less toxicity effect and residues in animal derived foods, was more potential growth-promoting and antibacterial property than olaquindox. Cytochrome P450 (CYP450) is the crucial metabolizing enzymes in the bodies. It is the most important effect for drug metabolization. In present study, the intention is to expound pharmacology mechanism, provide scientific reference for safe using and offer new idea for study of veterinary pharmacology and toxicology by analyzing activities of hepatic CYP450 isoenzymes and sub-type genes expression in rats administered kuianchun.The wistar rats were selected in the experiment, with similar health conditions, about 180±30g, and they were randomly divided into five groups including high dose group (Ⅰ), upper dose group (Ⅱ), middle dose group (Ⅲ) and low dose group (Ⅳ), and control group (C). Dissolving 99.97% kuianchun with 2% Tween-80 in distilled water to make suspension. Rats were administered 400, 200, 100, 50mg/kg-body weight (mg/kg·bw) kuianchun daily by orally for 7 days, respectively, and rats of the control group were given 0.9% NaCl solution. Preparing hepatic microsome, CYP450 content, cytochrome b5 (Cyt b5) content and activities of aminopyrine N-demethylase (APND), erythromycin N-demethylase (ERND), 7-ethoxyresorufin O-deethylase (EROD) of hepatic CYP450 isoenzymes in rats were determined by enzyme assay. After extracting hepatic mRNA, the sub-type genes expression of CYP1A1, CYP2E1 and CYP3A1 were examined by reverse transcription polymerase chain reaction (RT-PCR).Results: After the wistar rats were orally administered kuianchun 400, 200, 100, 50mg/kg·bw for 7 days, compared with the control group, the protein level of hepatic microsome increased with the drug dose upgrading. CYP450 content decreased markedly at doses of 100, 200, 400mg/kg·bw in male rats (P＜0.05), while increased at doses of 50, 100mg/kg·bw in female rats (P＜0.05); and the more of the dose and the less of CYP450 content. Cyt b5 content increased at doses of 100, 200, 400mg/kg·bw in male rats (P＜0.01), but the change of Cyt b5 content was not found in female rats. Activities of APND and ERND were lower than the control group at doses of 200, 400mg/kg·bw (P＜0.01), but activity of EROD was significantly higher than the control group (P＜0.01). A negtive correlation was observed between CYP450 changes and drug doses. Glutathione-S-transferase activity of liver microsome was higher at 50, 100mg/kg·bw than that of 200, 400mg/kg·bw groups. There were different changes of CYP450 activity between female and male rats. Compared with the control group, the expression of CYP2E1 and CYP3A1 mRNA lessened significantly at doses of 200,400mg/kg·bw(P＜0.01), and the expression of CYP1A1 mRNA at dose of 400mg/kg·bw reduced (P＜0.05). In addition, the sub-type genes expression of hepatic mRNA of CYP1A1, CYP2E1 and CYP3A1 also decreased in other groups, but there was no statistic difference.Conclusion: Hepatic CYP450 content, isoenzymes activities and the sub-type genes expression of mRNA of CYP1A1, CYP2E1, CYP3A1 may be inhibited by the high dose but it is not obvious at lower dose of kuianchun. There were different changes of CYP450 activity between female and male rats. Any potential toxicity and kickback will be not induced by Hepatic CYP450 if following the restrict of using kuianchun in clinical practice.