| 9178956 |
Bender AS, Woodbury DM, White HS: The rapid L- and D-aspartate uptake in cultured astrocytes. . Neurochem Res. 1997 Jun;22(6):721-6.
Astrocytes in primary culture possess a rapid L-aspartate saturable transport system (K (m) = 93 microM; V (max) = 81 nmol/min/mg protein), which shows certain stereospecificity since V (max) was 36% lower for D-aspartate uptake. These are values obtained at short incubation time (15 seconds), to obtain approximate initial rate conditions. Metabolic energy inhibitors, rotenone and iodoacetate very potently inhibited the L- and D-aspartate uptake processes, indicating that the transport process is an active one. However, the accumulation of L-aspartate was "enhanced" by inhibitors of L-aspartate metabolism, such as the aspartate aminotransferase inhibitor, aminooxyacetate and L-methionine sulfoximine, an inhibitor of glutamine synthetase, whereas D-aspartate (a non-metabolizable analog of L-aspartate) uptake was not affected. The accumulated levels of L-aspartate in the presence of aminooxyacetate were similar to the levels of D-aspartate. These effects of L-aspartate metabolic inhibitors, suggest that due to metabolism of the the L-aspartate, short incubation time (eg., 15 seconds) is necessary to measure the initial rate of L-aspartate uptake, in order to obtain the "true" kinetic parameters. |
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