NONDESTRUCTIVE MEASUREMENT OF RETINAL GLUCOSE-TRANSPORT AND CONSUMPTION IN-VIVO USING NMR-SPECTROSCOPY

The cellular events underlying various retinopathies are poorly unders tood but likely involve perturbation of retinal glucose metabolism. Cu rrent methods for assessing this metabolism are destructive, thus limi ting longitudinal studies. We hypothesize that following an intravitre ous injection, the clearance rate of a glucose analogue will be a nond estructive index of retinal glucose transport and metabolism in vivo. First, radiolabeled glucose analogues were injected into the vitreous. After 40 min, the dominant clearance path was posterior via the retin a and was consistent with a facilitated transport mechanism. Next, eit her [6,6-H-2(2)]glucose or 3-deoxy-3-fluoro-D-glucose was injected int o the vitreous of rabbit eyes, and the clearance rate of each analogue was determined over 40 min using, respectively, H-2 or F-19 NMR. Thes e rates were interpreted as a function of the retinal glucose transpor t and consumption. From the NMR data, the rate of retinal glucose cons umption was similar to 16 times slower than the transport of glucose. These data demonstrate that NMR measurements of glucose analogue clear ance rate from the vitreous can provide a nondestructive index of reti nal glucose transport and consumption in vivo.