Study of interaction between L-glutamate and human blood lymphocytes

The presence of specific glutamate receptors on T lymphocytes separated from normal human blood was investigated. Upon study of T lymphocytes interaction with [3H]glutamate the last one was found to bind specifically to these cells, Kd = 2.36 x 10(-7) M. Thirteen unlabelled compounds were tested as potential glutamate competitors. It was shown that only quisqualate (a structural analogue of glutamate) and dipeptides Ala-Glu, Glu-Ala, Glu-Glu competed with [3H]glutamate in binding to a common binding site. The experiments on binding of labelled and unlabelled glutamate bulky conjugates with dextran have demonstrated that both conjugated and free glutamate interacted with the common binding sites on the outer cell membrane. By this means it was shown that T lymphocytes exposed quisqualate-sensitive glutamate receptors on the outer surface of the plasma membrane.