Recently
developed high-throughput in vitro assays in combination
with computational models could provide alternatives to animal testing.
The purpose of the present study was to model the plasma, hepatic,
and renal pharmacokinetics of approximately 150 structurally varied
types of drugs, food components, and industrial chemicals after virtual
external oral dosing in rats and to determine the relationship between
the simulated internal concentrations in tissue/plasma and their lowest-observed-effect
levels. The model parameters were based on rat plasma data from the
literature and empirically determined pharmacokinetics measured after
oral administrations to rats carried out to evaluate hepatotoxic or
nephrotic potentials. To ensure that the analyzed substances exhibited
a broad diversity of chemical structures, their structure-based location
in the chemical space underwent projection onto a two-dimensional
plane, as reported previously, using generative topographic mapping.
A high-throughput in silico one-compartment model and a physiologically
based pharmacokinetic (PBPK) model consisting of chemical receptor
(gut), metabolizing (liver), central (main), and excreting (kidney)
compartments were developed in parallel. For 159 disparate chemicals,
the maximum plasma concentrations and the areas under the concentration–time
curves obtained by one-compartment models and modified simple PBPK
models were closely correlated. However, there were differences between
the PBPK modeled and empirically obtained hepatic/renal concentrations
and plasma maximal concentrations/areas under the concentration–time
curves of the 159 chemicals. For a few compounds, the lowest-observed-effect
levels were available for hepatotoxicity and nephrotoxicity in the
Hazard Evaluation Support System Integrated Platform in Japan. The
areas under the renal or hepatic concentration–time curves
estimated using PBPK modeling were inversely associated with these
lowest-observed-effect levels. Using PBPK forward dosimetry could
provide the plasma/tissue concentrations of drugs and chemicals after
oral dosing, thereby facilitating estimates of nephrotoxic or hepatotoxic
potential as a part of the risk assessment.