Abstract
Methionine participates in a large variety of metabolic pathways in brain, and its transport may play an important regulatory role. The properties of methionine uptake were examined in a preparation of neonatal rat brain astrocytes. Uptake is linear for 15 minutes, up to 2.5 μM. At steady state conditions, methionine is concentrated 30–50-fold. Measured methionine homoexchange accounts for a significant fraction of uptake at concentrations greater than 10 μM. We recently reported that methionine uptake is decreased by elevations in extracellular K+. Potassium induced efflux cannot account for this apparent effect; and thus for concentrations less than 2.5μM, and for short times of incubation, measured rates of methionine uptake represent unidirectional flux. At extracellular concentrations of K+ equal to 6.9 mM, the apparentV max of methionine transport is 182 pmol/min/mg protein, and theK m is 1.3 μM. Where K+ is shifted to 11.9 mM, theK m remains unchanged, and theV max is reduced by half.
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Cummins, C.J., Glover, R.A. & Sellinger, O.Z. Potassium modulation of methionine uptake in astrocytes in vitro. Neurochem Res 7, 637–644 (1982). https://doi.org/10.1007/BF00965129
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DOI: https://doi.org/10.1007/BF00965129