Effect of interferons on P-glycoprotein-mediated rhodamine-123 efflux in cultured rat hepatocytes.

The effect of interferon (IFN)-beta and IFN-gamma on P-glycoprotein (P-gp)-mediated efflux of rhodamin-123(Rho-123), a typical substrate of P-gp, was studied in rat hepatocytes in primary culture. After treatment with IFN-beta, IFN-gamma, or both for 3 days, steady-state levels of Rho-123, incorporated into the hepatocytes, were measured to evaluate the P-gp activity. Whereas IFN-beta did not affect the intracellular level of Rho-123, IFN-gamma treatment caused a significant increase of the level, suggesting that IFN-gamma treatment suppresses the expression of P-gp or its activity.