Metabolism of 2,6-dinitro[3-3H]toluene by human and rat liver microsomal and cytosolic fractions

Toxicokinetic Model Development for the Insensitive Munitions Component 2,4-Dinitroanisole

The Armed Forces are developing new explosives that are less susceptible to unintentional detonation (insensitive munitions [IMX]). 2,4-Dinitroanisole (DNAN) is a component of IMX. Toxicokinetic data for DNAN are required to support interpretation of toxicology studies and refinement of dose estimates for human risk assessment. Male Sprague-Dawley rats were dosed by gavage (5, 20, or 80 mg DNAN/kg), and blood and tissue samples were analyzed to determine the levels of DNAN and its metabolite 2,4-dinitrophenol (DNP). These data and data from the literature were used to develop preliminary physiologically based pharmacokinetic (PBPK) models. The model simulations indicated saturable metabolism of DNAN in rats at higher tested doses. The PBPK model was extrapolated to estimate the toxicokinetics of DNAN and DNP in humans, allowing the estimation of human-equivalent no-effect levels of DNAN exposure from no-observed adverse effect levels determined in laboratory animals, which may guide the selection of exposure limits for DNAN.

Characterization of the enzymes involved in thein vitrometabolism of amrubicin hydrochloride

The in vitro metabolism of amrubicin by rat and human liver microsomes and cytosol was examined. The main metabolic routes in both species were reductive deglycosylation and carbonyl group reduction in the side-chain. In vitro metabolism of amrubicinol by rat and human liver microsomes and cytosol was also examined and the main metabolic route of this active metabolite was reductive deglycosylation. Metabolism of amrubicin in human liver microsomes was inhibited by TlCl(3) and that in human liver cytosol was inhibited by dicumarol and quercetin. Generation of amrubicinol was inhibited only by quercetin. The results indicate that metabolism of amrubicin is mediated by NADPH-cytochrome P450 reductase, NADPH:quinone oxidoreductase and carbonyl reductase. In addition, generation of amrubicinol is mediated by carbonyl reductase. Metabolism of amrubicinol in human liver microsomes was inhibited by TlCl(3) and that in human liver cytosol was inhibited by dicumarol. The results indicate that metabolism of amrubicinol is mediated by NADPH-cytochrome P450 reductase and NADPH:quinone oxidoreductase. To investigate the influence of cisplatin on the metabolism of amrubicin and amrubicinol, human liver microsomes and cytosol were pre-incubated with cisplatin. This did not change the rates of amrubicin and amrubicinol metabolism in either human liver microsomes or cytosol.

Disposition of lantadene A, the pentacyclic triterpenoid hepatotoxin, orally administered to guinea pigs

Lantadene A (LA) administered orally to guinea pigs elicited cholestasis. LA could not be detected in liver, bile, gall bladder, blood and urine. LA and its biotransformation product reduced lantadene A (RLA) could be detected in caecum, large intestine, and faeces. In vitro incubation of LA with liver homogenates under aerobic and anaerobic conditions did not elicit its biotransformation to RLA. On the other hand, in vitro incubation of LA with guinea pig caecal and large intestinal contents under anaerobic conditions elicited conversion of LA to RLA. This is the first report of the biotransformation of LA in the animal system.