A PRELIMINARY PHYSIOLOGICALLY-BASED PHARMACOKINETIC MODEL FOR NAPHTHALENE AND NAPHTHALENE OXIDE IN MICE AND RATS

Naphthalene is a toxicant with unusual species and tissue specificity that has been the subject of in vitro studies. We describe a prelimina ry physiologically based pharmacokinetic (PBPK) model for naphthalene constructed solely from in vitro data for comparison to animal data wi thout the use of adjustable parameters. The prototypical PBPK model co ntaining five lumped tissue compartments was developed to describe the uptake and metabolism of naphthalene by mice and rats dosed intraperi toneally (ip) and orally (po). The model incorporates circulation and biotransformation of the semistable reactive intermediate, naphthalene oxide, as well as the parent compound naphthalene. Circulation is inc luded because the toxic action of naphthalene has been proposed to be caused by the formation of a reactive metabolite in one organ (liver) and its circulation to another organ (lung) being adversely affected b y the metabolite. The model allows conversion of naphthalene oxide int o dihydrodiol, glutathione (GSH) conjugates, 1-naphthol (nonenzymatica lly) and covalently bound adducts with proteins. Model simulations are compared with previously reported in vivo measurements of glutathione depletion, mercapturic acid formation, and covalently bound protein f ormation. The mouse model predicts accurately the amount of mercaptura tes excreted, the effect of various pretreatments, and the extent of c ovalent binding in the lung and liver resulting from ip administration , including the sharp increase in binding between 200 and 400 mg/kg.