title: A distributed-parameter model for formaldehyde uptake and disposition in the rat nasal lining.
abstract: DNA-protein cross-links (DPX) serve as a dosimeter for inhaled formaldehyde and are associated with tumor induction in rat nasal passages after chronic exposure to 6 ppm and above. To determine the role of epithelium-specific morphometry in formaldehyde-induced patterns of injury, we developed a mathematical model that links airflow-driven formaldehyde uptake with DPX formation in regions of the rat nose with high and low tumor incidence. A three-dimensional, anatomically accurate computational fluid dynamics model of rat nasal airflow and inhaled gas uptake was integrated with a physiologically based mathematical model incorporating tissue thickness, formaldehyde diffusion, its removal by enzymatic and nonenzymatic processes, and DNA distribution in the nasal mucosa to predict DPX formation. The model implicitly incorporates the reversible conversion of formaldehyde to methylene glycol. Where possible, parameter values were taken from the literature or estimated using published correlations. The Michaelis-Menten kinetic constants Vmax and Km, as well as a first-order constant for formaldehyde removal, were left as fitted parameters. The resultant model fit to the experimentally measured DPX in the high- and low-tumor-incidence regions of the rat nasal passages was very good. Sensitivity analysis indicates that among the fitted parameters, model fits are most sensitive to Vmax and that predictions were sensitive to changes in tissue thickness when all other parameters are held constant. The model structure facilitates extrapolation to primates and humans and application to other soluble, reactive gases.
authors.affiliation: CIIT Centers for Health Research, Research Triangle Park, North Carolina 27709, USA.
authors.forename: Anna V
authors.initials: AV
authors.lastname: Georgieva
authors.forename: Julia S
authors.initials: JS
authors.lastname: Kimbell
authors.forename: Paul M
authors.initials: PM
authors.lastname: Schlosser
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D018736:DNA Adducts / Q000032:analysis*; D004202:Disinfectants / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D005544:Forecasting; D005557:Formaldehyde / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D008962:Models, Theoretical; D009296:Nasal Cavity; D009297:Nasal Mucosa / Q000187:drug effects / Q000473:pathology; D051381:Rats; D012680:Sensitivity and Specificity
chemical_list: D018736:DNA Adducts; D004202:Disinfectants; D005557:Formaldehyde