Brain uptake of a food dye, erythrosin B, prevented by plasma protein binding

Although food colors have been held responsible for several behavioral disorders and do affect neuronal function when directly applied, there is no information on whether significant quantities of the dyes appear in the brain after consumption or parenteral administration. [14C]erythrosin B was administered directly into the circulation of mature rats and radioactivity was measured thereafter in brain regions at several times. Although insignificant parenchymal radioactivity was detected in brains perfused with dye in whole blood, significant concentrations of [14C]erythrosin B were detected in all brain regions when perfused with protein-free Ringers, as predicted from the octanol-water partition coefficient of the dye. Thus, significant brain uptake of intravascular dye is normally prevented by its binding to plasma protein (greater than 99% bound) and by the blood-brain barrier impermeability to the dye-protein complex. Sensitivity to food dyes such as erythrosin B in some individuals may reflect altered plasma protein binding capacity, which can vary with age and disease.