Transforming growth factors type beta inhibit multidrug transport in rat astrocyte cell lines

Astrocytes--like some endothelial cells of the blood-brain barrier--can express a multidrug transport system, which limits the intracellular accumulation of cytostatic agents and a variety of other substances. I observed that astrocytic multidrug transport can be modulated by cytokines: The transforming growth factors type beta 1, beta 2, and beta 1,2 are specific inhibitors of multidrug transport in fetal rat brain astrocyte cell lines. Other cytokines or interleukins did not inhibit astrocytic multidrug transport. Interestingly, the inhibitory effect of TGF-beta could be antagonized by the bone morphogenetic protein BMP 2, a cytokine that is distantly related to TGF-beta.