, 2006). Even when cultured with astrocytes or ACM, some of these porcine models are unable to achieve TEER comparable to our model. Furthermore,

permeability to [14C]sucrose in the present model is lower than or comparable to that of other porcine models. Immunochemical studies revealed clear marginal staining for occludin and claudin-5 in P.1 PBECs and edge staining in porcine brain microvessels, consistent with well-organised tight junctions. Functional assays confirmed the presence of the brain efflux transporter, P-gp and high levels of ALP activity in P.1 PBECs. Functional ALP has been reported in RBE4 cells ( Roux et al., 1994) and was increased when astrocyte-conditioned medium (ACM) and retinoic acid were used ( el Hafny et al., 1996). In our model, ALP activity in selleckchem P.1 PBECs without any astrocytic factors was over 20 times greater than in P.55 RBE4 cells. We chose RBE4 cells Cabozantinib manufacturer for comparison as this cell line is widely used and well characterised, and has been used in previous studies of ALP. The loss of activity in BBB enzymes such as ALP and gamma glutamyl transpeptidate in primary PBECs is well documented ( Beuckmann et al., 1995, Meyer et

al., 1990 and Meyer et al., 1991). Therefore, the comparison here demonstrates the quality of the present model, retaining ALP activity in culture even after seven days from isolation. Raising intracellular cAMP in P.1 PBECs could have contributed to the high level

of ALP activity in our model, as it has been shown that elevating cAMP can induce ALP activity in brain endothelial cells ( Beuckmann et al., 1995). Table 2 compares the basic characteristics achieved in this model, Celecoxib with three others from the literature: Franke et al. (2000), Zhang et al. (2006) and Smith et al. (2007). The selection of which method to use may be influenced by many factors, including the culture expertise of a group, models historically used, and the intended applications. The properties of the models are in many respects quite similar, adding to evidence that whatever the details of the preparative method, the confluent porcine brain endothelial model shows generally comparable behaviour, so that results from different studies can to some extent be pooled to form a growing database of information. Several methods have been described, but intra-batch and batch-to-batch variation was still a problem with many of them (Franke et al., 2000 and Zhang et al., 2006). There was some variability in the effects of adding serum, reported to either increase or decrease permeability (Nitz et al., 2003). The strengths of the present model are that it is relatively simple, involving fewer preparative steps: simply dissect out grey matter, homogenise, filter and digest to obtain brain microvessels. There are no complicated gradient separations. The model reliably gives tight brain endothelial cell monolayers without astrocyte influence.