Cell movement across, blood-brain barrier

Cell Movement Across the Blood-Brain Barrier.588... 

Cell Movement across the Blood-Brain Barrier... 

Figure 3.2. Potential mechanisms for drug movement across the blood-brain barrier. Routes of passage include passive diffusion through the brain capillary endothelial cells (A) utilization of inwardly directed (i.e. towards brain) transport or carrier systems expressed on brain capillary endothelial cells (B) utilization of outwardly directed (i.e. towards blood) efflux transport systems (C) or inclusion in various endocytic vesicular transport processes occurring within the brain capillary endothelial cells (D).

The main component of the blood-brain barrier is the brain endothelium, which exhibits a physical, an efflux and a metabolic barrier for the transport of drugs into the CNS. The physical barrier, an efflux, is a result of the tight junctions between adjacent endothelial cells, which are around 50-100 times tighter than in the peripheral endothelium, so that penetration across the endothelium is effectively confined to transcellular mechanisms [26, 27]. These junctions significantly restrict even the movement of small ions such as Na" " and Cl , so that the transendothelial electrical resistance (TEER), which is typically 2-20 2 cm in peripheral capillaries, can be over 1000 1 cm in brain endothelium [28]. 

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