Substrate-dependent regulation of ascorbate transport in astrocytes
- Univ. of Western Ontario, London (Canada)
Astrocytes possess a concentrative L-ascorbate (vitamin C) uptake mechanism involving a Na{sup +}-dependent L-ascorbate transporter in the plasma membrane. The present study examined the effects of ascorbate deprivation and supplementation on the activity of the transport system. Initial rates of L-ascorbate uptake were measured by incubating primary cultures of rat astrocytes with L-({sup 14}C)ascorbate for 1 minute at 37C. They observed that the maximal uptake rate, V{sub max}, rapidly (<3 hours) increased when cultured cells were deprived of L-ascorbate. There was no change in the apparent affinity (K{sub m}) of the transport system for ascorbate. V{sub max} returned to normal following addition of L-ascorbate, but not D-isoascorbate, to the medium. The authors conclude that astrocytes adapt ascorbate transport rates to changes in substrate availability. Furthermore, the data suggest that the transport system located in the astroglial plasma membrane regulates intracellular ascorbate concentration, because changes in transport rate may compensate for regional differences and temporal fluctuations in extracellular ascorbate levels.
- OSTI ID:
- 5488258
- Report Number(s):
- CONF-9004153-; CODEN: FAJOE
- Journal Information:
- FASEB Journal (Federation of American Societies for Experimental Biology); (United States), Vol. 4:3; Conference: 74. annual meeting of the Federation of American Societies for Experimental Biology, Washington, DC (United States), 1-5 Apr 1990; ISSN 0892-6638
- Country of Publication:
- United States
- Language:
- English
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