Planning and using PB-PK models: an integrated inhalation and distribution model for nickel

Area of Science:

• Toxicology and Environmental Health
• Mathematical Modeling in Biological Systems
• Pharmacokinetics and Risk Assessment

Background:

• Traditional toxicology experiments often lack robust interpretation frameworks for complex exposure scenarios.
• Extrapolating animal data to human health risks requires sophisticated modeling approaches.
• Understanding the kinetics of toxic substances like nickel is crucial for accurate risk assessment.

Purpose of the Study:

• To present a general method for using mathematical modeling in toxicology experiment design, execution, and interpretation.
• To illustrate the application of a physiologically based pharmacokinetic (PB-PK) dosimetry model for inhaled nickel in cancer risk estimation.
• To integrate lung and internal organ PB-PK models for comprehensive nickel fate assessment and human risk extrapolation.

Main Methods:

• Development of a PB-PK dosimetry model for inhaled nickel, integrating lung and systemic organ models.
• Utilizing the PB-PK model to design short-term and long-term animal experiments for parameter validation (Km, Vmax).
• Planning experiments, including constant infusion studies, to measure nickel distribution and elimination kinetics.

Main Results:

• Nickel removal from the lung was identified as saturable, following Michaelis-Menten kinetics.
• The integrated PB-PK model successfully estimated nickel's fate after inhalation.
• The model facilitated the calculation of human cancer risk estimates when combined with genotoxic data.

Conclusions:

• PB-PK models offer a powerful tool for designing and interpreting toxicology experiments, conserving animal use.
• This modeling approach aids in understanding physiological phenomena like saturable clearance and integrating in vitro/in vivo data.
• PB-PK models provide a robust framework for extrapolating toxicological findings to human health risks across multiple exposure routes.