Differential kinetics of glucose metabolism in porcine retinal and aortic endothelial cells.

Rates of glucose utilization, measured by steady state lactate production, and the rates of initial uptake of [14C]glucose were determined in cultured porcine retinal endothelial cells. The apparent Km for the steady state process proved to be lower than that determined for the uptake step (0.20 vs. 0.86 mmol/l glucose), suggesting that the carrier-mediated uptake of glucose into retinal endothelial cells cannot be the rate limiting step of overall glucose consumption. Thus, porcine retinal endothelial cells differ from porcine aortic endothelial cells, in that the aortic endothelial cell membrane acts as a barrier for the uptake of glucose into the cell. Accordingly, dexamethasone, which is known to reduce glucose uptake and degradation in aortic endothelial cells, does not influence glucose utilization in the retinal cells.