Oxidative stresses induced the cystine transport activity in human erythrocytes.

Cystine was transported into human erythrocytes in the presence of tertiary-butyl hydroperoxide (t-BH) or 1-chloro-2,4-dinitrobenzene (CDNB). The transport rate of cystine was dependent on the extracellular concentration of t-BH or CDNB, and on the incubation time. According to Dowex-1 column chromatography, the transported cystine was incorporated into fractions of glutathione disulfide (GSSG) and glutathione-S (GSH-S) conjugate. The transport of cystine was competitively inhibited by DL-homocystine and alanine. The inhibition rates by DL-homocystine and alanine were 75% and 68%, with similar Ki values of 0.7 mM and 0.6 mM, respectively. It is suggested that cystine transport is induced for glutathione synthesis when human erythrocytes are exposed to oxidative stresses. This transport system of cystine may serve as an emergency function in human erythrocytes.