Dataset Information

Metabolic profiling and in vitro-in vivo extrapolation of furathiocarb in mammalian hepatic microsomes.

ABSTRACT: Furathiocarb is a carbamate insecticide found in marine ecosystems as well as river water and sediments. The aim of this study was to characterize species differences in the in vitro metabolism of furathiocarb in seven mammalian species (human, monkey, minipig, rat, mouse, dog, rabbit) analyzed by LC-TOF-MS/MS, in order to provide qualitative and quantitative chemical-specific data to enhance toxicological risk assessment. Furathiocarb was mainly biotransformed to carbofuran metabolic pathway via (N-S) bond-cleavage. Two hydroxylated and sulfoxidated metabolites of furathiocarb were also detected (oxidation pathway). No unique human metabolites were detected. The carbofuran metabolic pathway was more predominant than the furathiocarb oxidation pathway in all species studied; differences based on hepatic clearance rates (CL _H ), were up to 9.4-fold in monkey and 7-fold in rats, while it was 4.3-fold in human. Animal to human differences in the carbofuran pathway are within the default toxicokinetic uncertainty factor, except for mouse (3.9-fold). Our findings on metabolic profiling and in vitro-in vivo extrapolations are helpful for the interpretation of toxicological findings and chemical risk assessment of furathiocarb.

SUBMITTER: Abass K

PROVIDER: S-EPMC9743442 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature

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Metabolic profiling and in vitro-in vivo extrapolation of furathiocarb in mammalian hepatic microsomes.

Abass Khaled K Reponen Petri P Alsanie Walaa F WF Rautio Arja A Pelkonen Olavi O

Toxicology reports 20220329

Furathiocarb is a carbamate insecticide found in marine ecosystems as well as river water and sediments. The aim of this study was to characterize species differences in the in vitro metabolism of furathiocarb in seven mammalian species (human, monkey, minipig, rat, mouse, dog, rabbit) analyzed by LC-TOF-MS/MS, in order to provide qualitative and quantitative chemical-specific data to enhance toxicological risk assessment. Furathiocarb was mainly biotransformed to carbofuran metabolic pat ...[more]

PMID: 36518466

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Project description:Hepatic in vitro biotransformation assays, in combination with in vitro-in vivo extrapolation (IVIVE) and bioaccumulation modeling, can be used to support regulatory bioaccumulation assessments. In most applications, however, these methods ignore the possibility of extrahepatic metabolism. Here we evaluated intestinal biotransformation in rainbow trout using S9 fractions prepared from the upper intestinal (GIT) epithelium. Measured levels of activity determined using standard substrates for phase I and phase II biotransformation enzymes were within 2-fold of activities measured in hepatic S9 fractions. In vitro intrinsic clearance rates for 2-ethylhexyl-4-methoxycinnamate (EHMC; an organic sunscreen agent) and two polycyclic aromatic hydrocarbons (pyrene [PYR] and benzo(a)pyrene [BAP]) were significantly higher in liver S9 fractions than in GIT S9 fractions. For octocrylene (OCT; a second sunscreen agent), however, in vitro intrinsic clearance rates were higher in GIT S9 fractions compared to liver S9 fractions. An existing 'liver only' IVIVE model was expanded to consider biotransformation in both the liver and GIT. Relevant IVIVE scaling factors were developed by morphological, histological, and biochemical evaluation of trout intestines. For chemicals biotransformed at higher rates by hepatic S9 fractions (i.e., BAP, PYR, EHMC), the 'liver & GIT' model yielded whole-body biotransformation rate constants (kMET) that were within 1.2 to 1.4-fold of those estimated using the 'liver only' model. In contrast to these findings, the mean kMET for OCT obtained using the 'liver & GIT' model was 3.3 times higher than the mean kMET derived using the 'liver only' model and was in good agreement with empirical kMET estimates determined previously for trout (<20 % difference). The results of this study suggest that current 'liver only' IVIVE approaches may underestimate in vivo biotransformation rates for chemicals that undergo substantial biotransformation in the GIT.

Project description:BackgroundThe developmental toxicity potential (dTP) concentration from the devTOX quickPredict (devTOXqP ) assay, a metabolomics-based human induced pluripotent stem cell assay, predicts a chemical's developmental toxicity potency. Here, in vitro to in vivo extrapolation (IVIVE) approaches were applied to address whether the devTOXqP assay could quantitatively predict in vivo developmental toxicity lowest effect levels (LELs) for the prototypical teratogen valproic acid (VPA) and a group of structural analogues.MethodsVPA and a series of structural analogues were tested with the devTOXqP assay to determine dTP concentration and we estimated the equivalent administered doses (EADs) that would lead to plasma concentrations equivalent to the in vitro dTP concentrations. The EADs were compared to the LELs in rat developmental toxicity studies, human clinical doses, and EADs reported using other in vitro assays. To evaluate the impact of different pharmacokinetic (PK) models on IVIVE outcomes, we compared EADs predicted using various open-source and commercially available PK and physiologically based PK (PBPK) models. To evaluate the effect of in vitro kinetics, an equilibrium distribution model was applied to translate dTP concentrations to free medium concentrations before subsequent IVIVE analyses.ResultsThe EAD estimates for the VPA analogues based on different PK/PBPK models were quantitatively similar to in vivo data from both rats and humans, where available, and the derived rank order of the chemicals was consistent with observed in vivo developmental toxicity. Different models were identified that provided accurate predictions for rat prenatal LELs and conservative estimates of human safe exposure. The impact of in vitro kinetics on EAD estimates is chemical-dependent. EADs from this study were within range of predicted doses from other in vitro and model organism data.ConclusionsThis study highlights the importance of pharmacokinetic considerations when using in vitro assays and demonstrates the utility of the devTOXqP human stem cell-based platform to quantitatively assess a chemical's developmental toxicity potency.

Dataset Information

Metabolic profiling and in vitro-in vivo extrapolation of furathiocarb in mammalian hepatic microsomes.

Publications

Metabolic profiling and <i>in vitro</i>-<i>in vivo</i> extrapolation of furathiocarb in mammalian hepatic microsomes.

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