Glutathione S ‐Conjugate Formation from 1‐Chloro‐2,4‐dinitrobenzene and Biliary S ‐Conjugate Excretion in the Perfused Rat Liver

1 The isolated hemoglobin‐free perfused rat liver was used as a model to study the formation of a glutathione S ‐conjugate and its disposition into the biliary as well as other extracellular (caval perfusate) compartments. 1‐Chloro‐2,4‐dinitrobenzene was chosen as substrate because it reacts with the glutathione‐ S ‐transferases at high activity to give rise to an S ‐conjugate, S ‐(2,4‐di‐nitrophenyl)‐glutathione, a product readily discernible from the parent compound. 2 S ‐(2,4‐Dinitrophenyl)‐glutathione formation rates were equal to the infusion rates of 1‐chloro‐2,4‐dinitrobenzene up to 0.3 μmol × min −1 × g liver −1 . Steady‐state rates of S ‐conjugate release were maintained until the glutathione content of the liver had decreased to about 40% of the control value. 3 Biliary excretion of the S ‐conjugate was practically quantitative at low rates of S ‐conjugate formation, up to about 30 nmol × min −1 × g liver −1 . and release of S ‐conjugate into the caval perfusate gradually increased with the rate of formation. Maximal biliary S ‐conjugate concentration was 36 mM. 4 Choleresis associated with biliary S ‐conjugate excretion amounted to 18.6 pi of extra bile per μmol of net S ‐conjugate excreted. This would correspond to a limiting concentration of 54 mM S ‐conjugate in the water compartment associated with biliary transport, e.g. exocytotic vesicle in the context of an exocytosis‐like mechanism of bile formation. 5 The system described here is suited for further investigation of properties of bile formation, as is illustrated by the sensitive detection of changes in the concentration of S ‐conjugate in the perfusate upon Ca 2+ ‐depletion.