Preferential glutamine uptake in rat brain synaptic mitochondria

Glutamine uptake has been studied in purified rat brain mitochondria of synaptic or non-synaptic origin. It was taken up by an active saturable transport mechanism, with an affinity two-times higher in synaptic than in non-synaptic mitochondria (K _m = 0.45 and 0.94 mM, respectively), V _max of uptake was 7-times higher in synaptic mitochondria (V _max = 9.2 and 1.3 per mg protein, respectively). Glutamine transport was found to be inhibited by L-glutamate (IC₅₀ = 0.64 mM) as well as thiol reagents (mersalyl, N-ethylmaleimide). It is suggested that differential uptake of glutamine in mitochondria of synaptic or nonsynaptic origin may be a major mechanism in the regulation of the synthesis of the neurotransmitter glutamate.