Glutamate accumulation by human gliomas and meningiomas in tissue culture

The rapid accumulation of radioactive glutamate was studied in human brain tumor cells grown in tissue culture. The MGH-LM line of human astrocytoma demonstrated both a high (apparent Km = 20 μM) and a low (apparent Km = 0.2mM) affinity component for the uptake of glutamate. The high affinity component was sodium-, temperature-, and energy-dependent and was present during the confluent (stationary) but not the log phase of cell growth. A study of confluent monolayer cultures of several other human brain tumors revealed that a similar high affinity uptake of glutamate occurred in 7 out of 8 malignant astrocytomas and appeared to be independent of the grade of malignancy. In 3 optic gliomas and 5 meningiomas studied, low but not high affinity uptake of glutamate was found. These studies suggest that glial cells in the human brain may in some instances possess uptake characteristics for glutamate similar to those previously ascribed to nerve endings.