The Importance of Conjugation with Glutathione for Sulfobromophthalein Sodium (BSP) Transfer from Blood to Bile*

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Abstract
The components of the hepatic BSP-glutathione conjugating system were altered by feeding rats a protein-free diet or a protein-free diet supplemented with 1% cystine. After 2 dyas, liver glutathione, the substrate for BSP conjugation, fell approximately 80 and 33% on the respective diets. Activity of the enzyme that catalyzes BSP-glutathione conjugation decreased 25%, approximately to the same extent in rats maintained on the two diets. After intravenous administration of dye, excretion of BSP into bile was decreased due to diminished excretion of conjugated BSP in the rats fed a protein-free diet for 2 days. Biliary excretion of conjugated, and thus total BSP, was restored to maximal control levels when hepatic glutathione levels were bolstered by feeding the protein-free diet supplemented with 1% cystine. The data indicate that intrahepatic conjugation of BSP with glutathione exerts an important effect on BSP excretion into bile. Although conjugation does not appear to affect hepatic uptake of BSP directly, conjugation does appear to affect the maximal rate at which BSP is transported from liver cells into bile, conjugated BSP being transported more rapidly into bile.