Marked increase of cysteine levels in many regions of the brain after administration of 2-oxothiazolidine-4-carboxylate.

Although brain cysteine levels can be increased by administration of cysteine, treatment with this amino acid causes toxicity. L-2-Oxothiazolidine-4-carboxylate, a compound in which the thiol group is masked, is effectively transported into the mouse and rat brain. It is converted intracellularly by the action of 5-oxoprolinase into L-cysteine. Study of various regions of the rat brain (cerebellum, hypothalamus, cortex, brain stem, pons, caudate nucleus) showed that the levels of cysteine increased significantly after administration of L-2-oxothiazolidine-4-carboxylate. Glutathione levels were not increased or were only slightly increased under these conditions, reflecting the low rate of glutathione synthesis in many regions of the brain.