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

摘要

>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 class="smallCaps">d- and class="smallCaps">l-aspartate, class="smallCaps">d- and class="smallCaps">l-thero-3-hydroxyaspartate and class="smallCaps">l-trans-pyrrolidine-2,4-dicarboxylate but not class="smallCaps">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 (V_max) of [3H] class="smallCaps">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.