Predicting maternal rat and pup exposures: how different are they?

Area of Science:

• Pharmacokinetics and Toxicology
• Developmental Biology
• Environmental Health

Background:

• Cross-species extrapolation for early life chemical exposures requires accurate dosimetry in young.
• Maternal exposure dose is often used for extrapolation, introducing significant uncertainty in risk assessments.
• Understanding chemical dosimetry in neonates and pups is vital for safety evaluations.

Purpose of the Study:

• To develop a pharmacokinetic model predicting chemical dosimetry in young animals.
• To evaluate the impact of various dosing strategies and chemical properties on pup exposure.
• To improve the accuracy of extrapolating toxicity findings from animal studies to humans.

Main Methods:

• A compartmental pharmacokinetic model was developed, incorporating lactation and postnatal biological factors.
• The model simulated adult pharmacokinetics, milk distribution, and postnatal biology.
• Three dosing strategies (gavage, constant diet, adjusted diet) and varying pharmacokinetic properties were analyzed.

Main Results:

• Pup exposure doses frequently differ from maternal doses.
• Factors like half-life, milk transfer, volume of distribution, and dosing route significantly influence pup exposure.
• Model predictions showed pup exposure is generally lower than maternal with shorter half-life, lower milk transfer, larger volume of distribution, and gavage dosing.

Conclusions:

• The developed pharmacokinetic model accurately predicts chemical dosimetry in young animals.
• Pup exposures do not always mirror maternal exposures, highlighting limitations of using maternal dose alone.
• Model predictions can inform the design and interpretation of early life toxicity and pharmacokinetic studies.