Reduced ocular glucose transport and increased non-electrolyte permeability in rats with retinal degeneration (RCS)

The transport kinetics across the plasma-ocular barriers of labeled molecules including urea, D-glucose, 3-0-methyl-D-glucose, L-glucose, and sucrose were studied in adult RCS rats and compared to control albino Sprague-Dawleys (SD). Results indicate that substances that passively cross the plasma-aqueous and plasma-vitreous barriers (urea, sucrose, L-glucose) do so more readily in the RCS rat especially via the trans-retinal route. By contrast, D-glucose, which penetrates the ocular barriers of the control rat by a carrier-mediated mechanism was found to cross the ocular barriers of the RCS rat at a reduced rate. Thus, the ocular barriers of the RCS rat with well developed retinal degeneration demonstrate an increase in passive permeability and a reduction in ability to perform their membrane transport function (D-glucose). The permeability defect was more pronounced in the blood-vitreous barrier than in the blood-aqueous barrier.