RT Journal Article SR Electronic T1 Localization of glutathione conjugation activities toward bromosulfophthalein in perfused rat liver. Studies with the multiple indicator dilution technique. JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 1070 OP 1078 VO 21 IS 6 A1 Y Zhao A1 C A Snel A1 G J Mulder A1 K S Pang YR 1993 UL http://dmd.aspetjournals.org/content/21/6/1070.abstract AB The plasma binding and conjugation kinetics of bromosulfophthalein (BSP) with glutathione (GSH) were studied in the single-pass in situ perfused rat liver (portal vein perfusion at 10 ml/min); GSH in postmitochondrial fractions of the liver at the end of the experiment was examined as a potential rate-determining factor. BSP was highly bound to 1% albumin with at least two classes of binding sites: one of 0.17 site with an association constant of 1.9 x 10(7) M-1, and one of 7.4 equivalent sites of association constant, 1.3 x 10(5) M-1. Nonlinear binding was observed within between 5-1500 microM BSP. At varying input concentrations (0.4-250 microM) of BSP, the unbound fraction was extremely low (< 0.005) and the hepatic extraction ratio declined from 0.67 to 0.15; loss of BSP was primarily caused by GSH conjugation to form BSP-GSH, which appeared exclusively in bile. Additionally, unchanged BSP and two very minor unidentified metabolites were also excreted in bile. The formation of BSP-GSH proceeded with an apparent Vmax of 22 nmol/min/g and a KM of 0.05 microM, whereas the parameters for BSP excretion were 0.85 nmol/min/g and 0.02 microM, respectively. Within the concentration range of BSP examined, GSH availability did not appear to be rate-limiting in the formation or excretion of BSP-GSH.(ABSTRACT TRUNCATED AT 250 WORDS)