Inhibition of glutathione efflux in the recirculating rat liver perfusion by cysteine but not by oxothiazolidine carboxylate, an intracellular cysteine precursor.

In the recirculating rat liver perfusion a continuous release of glutathione into the perfusion medium is observed. Addition of L-cysteine to the perfusion medium immediately arrested this glutathione efflux. The cysteine precursor oxothiazolidine carboxylate did not block the glutathione efflux in spite of the fact that it generated more L-cysteine inside the liver cells than L-cysteine itself; L-cysteine is rapidly oxidized to cystine, that is no longer taken up by the liver. The results suggest that the inhibition of glutathione efflux results from the presence of cystine in the perfusion medium.