Na+‐dependent high affinity uptake of l‐glutamate in primary cultures of human fibroblasts isolated from three different types of tissue

Abstract
Cultured human fibroblasts isolated from embryonic muscle, skin and peripheral nerve tissues were found to accumulate [3H]L‐glutamate by a Na+‐dependent uptake process strongly inhibited by several glutamate/aspartate analogues including d‐ and l‐aspartate, d‐ and l‐thero‐3‐hydroxyaspartate and l‐trans‐pyrrolidine‐2,4‐dicarboxylate but not d‐glutamate. It was also reduced by elevated concentrations of K+, Rb+ and Cs+. The values of K m 's were 5–20 μM, well within the ‘high affinity’ region. Variations in the capacity (Vmax) of [3H]l‐glutamate uptake did not correlate with the origin (muscle, skin or nerve tissue) of the fibroblasts. The uptake characteristics suggest that it is mediated by a transport system similar to that commonly observed only in brain tissue.

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