[Modulation on the P-glycoprotein in the jejunum by combined use of Glycyrrhiza inflata and Kansui].

To investigate the modulation on the P-glycoprotein in the jejunum by combined use of Glycyrrhiza inflata and Kansui with ussing chamber and rt-pcr, Rhodamine 123 (R123), a P-gp substrate and fluorescein sodium (CF), a model drug of non-P-gp substrate transported by a passive diffusion were taken as investigational drugs. Because these two drugs can be easily assayed and widely used in various research fields. The permeability of R123 or CF via Wistar rat jejunum membranes was evaluated by in vitro ussing chamber after oral administration of four different decoctions of Glycyrrhiza inflata and Kansui for 1 week. And the concentration of R123 or CF was determined by the fluorospectrophotometry in the receiving solution. Meanwhile the expression of mdr1a in P-glycoprotein was detected by real-time fluorescent quantitative PCR. After oral administration of combined decoction of the single drug, the absorptive directed permeability of R123 increased significantly (P < 0.01). On the other hand, Kansui and combine decoction of the two drugs also decrease the permeability of secretory directed transport (P < 0.05). No action of Glycyrrhiza inflata was found on the secretory transport of R123 [Papp = (2.56 +/- 0.38) x 10(-5), cm x s(-1)] across the jejunum tissues, while Papp of control group was found [Papp = (2.35 +/- 0.27) x 10(-5), cm x s(-1)]. After oral administration of Kansui decoction for 1 week and 2 weeks, the levels of mdr1a expression in Wistar rats were lower than that of the control group, but there were no significant difference in the results. Meanwhile, Glycyrrhiza inflata had no effect on transport of CF across the jejunum tissues, though the other three groups could decrease the permeability of CF, as compared with control group. Kansui may slightly inhibit P-glycoprotein function in the intestinal membrane. For another, some compositions in Kansui inhibit P-glycoprotein function, and some others strengthen the tight junction between cells in the intestinal membrane to decrease permeability of CF. As the inhibitory action to P-glycoprotein was enhanced by combination of Glycyrrhiza inflata and Kansui, based on the results, it may be one of the mechanisms of creating toxicity once co-administration of Glycyrrhiza inflata and Kansui.

[Effect of Glycyrrhiza inflata and Daphne genkwa on permeabilities of rhodamine 123, a P-glycoprotein substrate across rat jejunum membranes in vitro].

OBJECTIVE: To investigate the modulation of Glycyrrhiza inflata and Daphne genkwa on the permeability characteristics of rhodamine 123 (R123), one P-glycoprotein (P-gp) substrate, across the jejunum membranes. And then approach the possible permeability mechanism of the drugs after co-administration of G. inflata and D. genkwa in gastrointestinal tract. METHOD: The permeability of R123 or fluorescein sodium (CF) via Wistar rat jejunum membranes was evaluated by in vitro diffusion chamber system after oral administration of four different decoctions and 0.9% sodium chloride (20 mL x kg(-1)) for 1 week. And the concentration of R123 or CF was determined by the fluorospectrophotometry. The apparent permeability coefficient (P(app)) was calculated by the equation P(app) = dQ/d(t) x (1/A x C0), where P(app) was expressed in cm/s, dQ/dT was the slope of the linear portion of the permeation curves, A was the diffusion area, and C0 was the initial concentration of rebamipide in the donor side, and then compare their differences were compared with control group. RESULT: After oral administration of G. inflata decoction, D. genkwa decoction and decoction of the combination of the previous decoctions, the absorptive directed transport of R123 was significantly increased (P < 0.05, compared with control group). On the other hand, D. genkwa could also decrease the permeability of secretory directed transport (P(app) = 2.98 +/- 0.59), while no action of G. inflata was found on the secretory transport of R123 ( P(app) = 5.24 +/- 3.98) across the jejunum tissues, while P(app) of control group was 4.38 +/- 1.18. Meanwhile, G. inflata had no effect on transport of CF across the jejunum tissues, though the other three groups could decrease the permeability of CF, as compared with control group. CONCLUSION: G. inflata may slightly inhibit P-glycoprotein function in the intestinal membrane, while D. genkwa may be a relatively strong inhibitor of P-gp. For another, some compositions in D. genkwa inhibit P-gp function, and some others strengthen the tight junction between cells in the intestinal membrane to decrease permeability of CF. As the inhibitory action to P-gp was enhanced by combination of G. inflata and D. genkwa, based on the results, it may be one of the mechanisms of creating toxicity once co-administration of G. inflata and D. genkwa.