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M Khatami, W Y Li, J H Rockey; Kinetics of ascorbate transport by cultured retinal capillary pericytes. Inhibition by glucose.. Invest. Ophthalmol. Vis. Sci. 1986;27(11):1665-1671.
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Accumulation of radioactive L-[carboxyl-14C]-ascorbic acid by cultured bovine retinal capillary pericytes was studied. Kinetic analysis of the transport showed a time-dependent, saturable system with an apparent Km of 76.0 microM and a Vmax of 42 pmole/micrograms DNA/min. A facilitated carrier diffusion process was established on the basis that the system was not sensitive to 2,4-dinitrophenol, ouabain, or reduced sodium concentration in the incubation media, and that the carrier system demonstrated stereospecificity for an ascorbate analogue, dehydroascorbate, and for sugar analogues such as alpha-D-glucose and 3-0-methyl-D-glucose (3-0-MG), but not for beta-D-fructose or L-glucose. Transport of ascorbate by cultured pericytes was insulin-insensitive. 3-0-Methyl-D-glucose inhibited ascorbate transport into pericytes in a non-competitive manner with a Ki of 22 mM. These results indicate that, in cultured retinal capillary pericytes, a common facilitated carrier diffusion system is involved in the transport of ascorbate and sugar analogues such as alpha-D-glucose or 3-0-MG.
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