Blood-brain barrier glucose diffusion

Facilitated diffusion of glucose across the blood-brain barrier and into brain cells is catalyzed by GLUT1,- 2 and -3, products of the SLC2 gene superfamily 90... 

The other major class of transporter protein is the carrier protein. A prototypic example of a carrier protein is the large neutral amino acid transporter. An important function of the LNAA transporter is to transport molecules across the blood-brain barrier. As discussed previously, most compounds cross the BBB by passive diffusion. However, the brain requires certain compounds that are incapable of freely diffusing across the BBB phenylalanine and glucose are two major examples of such compounds. The LNAA serves to carry phenylalanine across the BBB and into the central nervous system. Carrier proteins, such as the LNAA transporter, can be exploited in drug design. For example, highly polar molecules will not diffuse across the BBB. However, if the pharmacophore of this polar molecule is covalently bonded to another molecule which is a substrate for the LNAA, then it is possible that the pharmacophore will be delivered across the BBB by hitching a ride on the transported molecule. 

As originally formulated (5) the parameter a represents the ratio of unidirectional fluxes of a compoimd across the blood-brain barrier. In the case of a compound like glucose, which passes the blood-brain barrier by carrier mediated facilitated diffusion, (1 + Km/Ct)/(1 + Km/Cb),... 

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