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, 23 (4), 447-56

In Situ Kinetics of Glucose Transport Across the Blood-Retinal Barrier in Normal Rats and Rats With Streptozocin-Induced Diabetes

  • PMID: 7118504

In Situ Kinetics of Glucose Transport Across the Blood-Retinal Barrier in Normal Rats and Rats With Streptozocin-Induced Diabetes

S R Ennis et al. Invest Ophthalmol Vis Sci.

Abstract

Glucose transport across the blood-retinal barrier (BRB) was investigated in situ by means of a modification of the single-injection technique developed for studying transport across the blood-brain barrier. A retinal uptake index was calculated from the fractional extraction for 14C-glucose divided by the fractional extraction for the 3H2O reference. The use of the Eadie-Hofstee transformation to determine the Km of carrier-mediated transport revealed at least two transport systems for the unidirectional glucose flux across the BRB. Control data showed a relatively high-affinity system with a Km of 0.24 mM and a lower affinity system with a Km of 7.81 mM. Both these transport systems have been shown to be sensitive to phloretin but not to phloridzin or acetazolamide. It has also been shown that glucose transport is uneffected by Na+ or K+ concentrations but that calcium does have a significant effect on the lower affinity transport system for glucose. We have also demonstrated that the Km values of both transport systems are significantly increased by 2 months of streptozocin-induced diabetes.

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