Temporal expression of transporters and receptors in a rat primary co-culture blood-brain barrier model.

1. The more relevant primary co-cultures of brain microvessel endothelial cells and astrocytes (BMEC) are less utilized for screening of potential CNS uptake when compared to intestinal and renal cell lines. 2. In this study, we characterized the temporal mRNA expression of major CNS transporters and receptors, including the transporter regulators Pxr, Ahr and Car in a rat BMEC co-cultured model. Permeability was compared with the Madin-Darby canine kidney (MDCKII)-MDR1 cell line and rat brain in situ perfusion model. 3. Our data demonstrated differential changes in expression of individual transporters and receptors over the culture period. Expression of ATP-binding cassette transporters was better retained than that of solute carrier transporters. The insulin receptor (IR) was best maintained among investigated receptors. AhR demonstrated high mRNA expression in rat brain capillaries and expression was better retained than Pxr or Car in culture. Mdr1b expression was up-regulated during primary culture, albeit Mdr1a mRNA levels were much higher. P-gp and Bcrp-1 were highly expressed and functional in this in vitro system. 4. Permeability measurements with 18 CNS marketed drugs demonstrated weak correlation between rBMEC model and rat in situ permeability and moderate correlation with MDCKII-MDR1 cells. 5. We have provided appropriate methodologies, as well as detailed and quantitative characterization data to facilitate improved understanding and rational use of this in vitro rat BBB model.