The uptake index method applied to studies on the blood-retinal barrier. II. Transport of several hexoses by a common carrier.

The uptake index method was used for studies on the passage of various monosaccharides across the blood-retinal and the blood-brain barriers in albino rats. The results indicate large similarities for the hexose transport through the two barriers. Thus a stereo-specific, saturable transport of glucose was observed for both barriers. The carriers involved showed measurable affinity for 2-deoxy-D-glucose, 3-0-methyl-D-glucose, D-mannose and D-galactose, but not for L-glucose, D-fructose or D-ribose. The relative affinities of the various hexoses to the carriers were similar. Phloretin and phloridzin both reduced retinal and brain uptake of D-glucose.