The organic dye sulfobromophthalein is rapidly taken up and conjugated with glutathione by isolated hepatocytes. To examine whether intracellular conjugation influences the preceding uptake process of the organic dye, conjugation was blocked by depleting cellular glutathione with styrene oxide. Complete inhibition of the conjugation step did not affect initial rates of uptake of 5 and 10 microM sulfobromophthalein. Moreover the maximal cellular accumulation of the dye in glutathione-depleted hepatocytes representing almost exclusively free sulfobromophthalein is similar to the transient maximum concentration of the organic anion found with untreated cells where conjugation takes place. In the case of the untreated cells maximal accumulation is attained at about 20 min, thereafter intracellular levels decrease due to the release of sulfobromophthalein-glutathione conjugate into the medium.