(1) Compartmentation of glutamate metabolism in brain cortex previously observed only in vivo, has now been demonstrated in vitro.This was shown by using [U-14C]aspartate and [U-14C]glutamate as tracer substrates.
(2) Preparation and maintenance of the slices at 0° resulted in reversible inhibition of glutamine synthesis. Preincubation at 37° for 10 min or preparation of the slices at room temperature partially overcame this inhibition.
(3) Transfer to fresh medium after preincubation had an added stimulatory effect on glutamine synthesis.
(4) Incubation in high K+ medium (27 mm) altered the relative specific activity of glutamine.
(5) The data are in keeping with the postulate of the existence of at least two different pools of citric acid cycle intermediates in the cerebral cortex.