Abstract: AIM: To study the effects of berberine chloride (Ber) and co-administration with cyclosporin (CsA) on CYP3A1 in rat liver and small intestine. METHODS: The rats were randomly divided into 7 groups: control group, 150 mg·kg^-1 ketoconazole, 100 mg·kg^-1 Ber, 200 mg·kg^-1 Ber, 45 mg·kg^-1CsA, 100 mg·kg^-1Ber co-administrated with 45 mg·kg^-1CsA, and 200 mg·kg^-1 Ber co-administrated with 45 mg·kg^-1CsA.The levels of CYP3A1 in rat liver and small intestine were assayed by RT-PCR and Western blot. RESULTS: After administration for 12 d, all drug administration groups, except 100 mg·kg^-1 Ber, had significant inhibitory effects on the mRNA levels of CYP3A1 by RTPCR analysis in the liver.The analysis of Western blot showed that 200 mg·kg^-1 Ber co-administrated with 45 mg·kg^-1CsA for 6d exhibited the inhibitory action on CYP3A1 in the liver.Moreover, 100 mg·kg^-1Ber co-administrated with 45 mg·kg^-1 CsA and 200 mg·kg^-1 Ber co-administrated with 45 mg·kg^-1 CsA for 12 d could markedly inhibit the expression of CYP3A1 by Western blot analysis in both liver and small intestine. CONCLUSION: The mechanism on the increase of CsA concentration by Ber may be that Ber intensifies the inhibitory effects of CsA on CYP3A1 to reduce the metabolism and elimination of CsA in liver and small intestine.

Key words: berberine chloride, cyclosporin, cytochrome P450, reverse transcriptase-polymerase chain reaction, Western blot