Using a semi-targeted approach, we have investigated the effect of
acetaminophen on circulating
bile acid profiles in rats, including many known
bile acids and potential isomeric structures, as well as
glucuronide and
sulfate conjugates. The chromatographic separation was based on an optimized reverse-phase method exhibiting excellent resolution for a complex mix of
bile acids using a solid-core C18 column, coupled to a high-resolution quadrupole time-of-flight system. The semi-targeted workflow consisted of first assigning all peaks detectable in samples from 46 known
bile acids contained in a standard mix, as well as additional peaks for other
bile acid isomers. The presence of
glucuronide and
sulfate conjugates was also examined based on their elemental formulae and detectable peaks with matching exact masses were added to the list of features for statistical analysis. In this study, rats were administered
acetaminophen at four different doses, from 75 to 600 mg/kg, with the highest dose being a good model of
drug-induced liver injury. Statistically significant changes were found by comparing
bile acid profiles between dosing levels. Some tentatively assigned conjugates were further elucidated using in vitro metabolism incubations with rat liver fractions and standard
bile acids. Overall, 13 identified
bile acids, 23 tentatively assigned
bile acid isomers, and 9
sulfate conjugates were found to increase significantly at the highest
acetaminophen dose, and thus could be linked to
drug-induced liver injury.