18β-glycyrrhetinic Acid Induces UDP-glucuronosyltransferase in Rats

UDP-glucuronosyltransferase (UDP) catalyzes a broad spectrum of endobiotic and xenobiotics. It is the isoform of the UGT1 family, which are made from the complex gene locus by an alternative combination of one of the unique first exons with the commonly used exons. UDP is believed to be involved in cellular activity and signaling process associated with detoxification. In this study, rats were orally administered with 18 beta-glycyrrhetinic acid (GA) for four weeks before rats were sacrificed. The mRNA was extracted from the liver and cDNA was prepared by reverse transcription method. By PCR and Northern blot analysis, UGT1A8 mRNA level was found to be increased in the treatment group (P < 0.05). The results showed that the mRNA expression of UGT1A8 could be induced both by GA and the licorice extract. GA was identified to be the active component of the aqueous extract of licorice responsible for induction of UGT1A8 in the rat liver. The results suggest a transcriptional control of the UGT1A8 synthesis can be modulated by phytochemicals in the rat liver. The increased UDP activity could enhance detoxification of toxicants.