Thiol-Disulfide Effects on Hepatic Glutathione Transport Studies in Cultured Rat Hepatocytes and Perfused Livers

In cultured rat hepatocytes, cystine led to an inhibition ofGSH efflux by lowering the V.,,. by- 35 % without affecting the K,. The cystine-mediated inhibition of GSH efflux was rapid in onset (< 1 h), with near maximum effect at 0.1 mM. Inhibi-tion was still observed when cystine uptake was prevented. Cys-tine and sulfobromophthalein-GSH, a selective inhibitor of si-nusoidal transport of GSH, did not exhibit additive inhibitory effects on GSH efflux. Depletion ofATP or membrane depolar-ization after cystine treatment were excluded as potential mech-anisms. DT1 not only reversed the cystine-mediated inhibition of GSH efflux, it stimulated GSH efflux up to 400-500%. The DTT effect was immediate in onset, reaching maximum after 30 min, and was partially reversed by cystine, suggesting that the two share a common site(s) of action. DTT treatment did not alter cellular ATP levels or change the membrane potential. In cultured hepatocytes, D1T treatment increased the V, of GSH efflux by- 500 % without affecting the K.. Inhibition of microtubular function and vesicular acidification did not affect basal or DT ' stimulated efflux. Both cystine and DTT effects on sinusoidal GSH efflux were confirmed in perfused livers. In summary, the capacity of the sinusoidal GSH transporter is markedly influenced by thiol-disulfide status. (J. Clin. Invest