ABSTRACT
Aim To investigate effects of berberine (Ber) on the transport of P-gp substrates including cyclosporine A (CsA) and digoxin across Caco-2 and L-MDR cell monolayers. Methods Permeability coefficients and transport rates of digoxin and CsA across Caco-2 and L-MDR1 monolayers were measured in the presence of Ber(50 ?mol?L-1~5 mmol?L-1). Results The inhibition studies for digoxin transport showed a dose-dependent decrease in basal-to-apical direction across Caco-2 and L-MDR1 monolayers in the presence of Ber (50 ?mol?L-1~5 mmol?L-1). Both a dose-dependent decrease in basal-to-apical direction and an increase in apical-to-basal direction were observed for CsA transport across Caco-2 monolayers with different concentrations of Ber. The IC50 values calculated for Ber-induced inhibition of digoxin transport are 1.44 mmol?L-1 in Caco-2 cells and 1.24 mmol?L-1 in L-MDR1 cells, respectively. The IC50 value for Ber-induced inhibition of CsA transport is 607 ?mol?L-1 in Caco-2 cells. Conclusion It was suggested that the inhibition and saturation of P-gp transport activity might be involved in interactions between Ber and CsA.