Biliary excretion and intestinal metabolism in the intermediary metabolism of pentachlorothioanisole.

1. Biliary metabolites from rats dosed with pentachlorothioanisole (PCTA) were characterized by fast atom bombardment mass spectrometry and electron impact mass spectrometry. 2. Most of the biliary metabolites from PCTA were mercapturic acid pathway metabolites of methylsulphinyltetrachlorobenzene (51% of the dose); the remaining characterized biliary metabolites (20%) were mainly methylsulphinyltetrachlorothiophenols excreted as unknown conjugates. 3. Pathways are proposed for the intermediary metabolism of PCTA to bis-(methylthio)tetrachlorobenzene (bis-MTTCB) involving glutathione conjugation, biliary excretion, intestinal metabolism, and enterohepatic circulation.