OBJECTIVEThe aim of the present study was to evaluate the modulating effect of glycyrrhizic acid C-18 epimers, 18alpha-glycyrrhizic acid (alpha-GL) and 18beta-glycyrrhizic acid (beta-GL) on both P-glycoprotein (P-gp) activity and expression in Caco-2 cell.

METHODThe effects of P-gp activity were analyzed by rhodamine (Rhd 123) accumulation test, and those of P-gp expression were analyzed by flow cytometry and real-time PCR.

RESULTAt middle and high concentrations (10, 60 micromol x L(-1)), alpha-GL inhibited the function of P-gp and with on dose dependent while beta-GL induced the function of P-gp at three test concentrations with no dose dependent too. At middle and high concentrations (10, 60 micromol x L(-1)), alpha-GL down-regulated the expression of MDR1 mRNA. At high concentrations (60 micromol x L(-1)), beta-GL up-regulated the expression of MDR1 mRNA; At high concentrations (60 micromol x L(-1)), beta-GL induced the expression of P-gp protein while alpha-GL has no effect on the expression of P-gp protein at three test concentrations.

CONCLUSIONThe effects of alpha-GL and beta-GL on the expression of MDR1 mRNA and CYP3A mRNA showed the same trend. The character that epimers of GL act on CYP3A and P-gp show similar stereo selectivity whether relate to PXR need further study.

ATP Binding Cassette Transporter, Sub-Family B ; genetics ; metabolism ; Caco-2 Cells ; Down-Regulation ; drug effects ; Drugs, Chinese Herbal ; pharmacology ; Gene Expression ; drug effects ; Glycyrrhizic Acid ; chemistry ; pharmacology ; Humans

AIM: To evaluate the bioequivalence of cinacalcet hydrochloride tablets in healthy Chinese volunteers. METHODS: A randomized, open, double-period and crossover trial was conducted, 48 healthy volunteers were administered a single dose of cinacalcet test tablets or reference tablets orally under each fasting and fed condition. The concentration of cinacalcet was determined by validated LC-MS/MS method. Pharmacokinetic parameters were calculated by Phoenix WinNonlin 8.0 to study its bioequivalence. RESULTS: The main pharmacokinetic parameters of test tablets and reference tablets under fasting condition were as follows: C