title: Deposition and clearance of a water-reactive vapor, methylphosphonic difluoride (difluoro), inhaled by rats.
abstract: Rats were exposed by both inhalation and noninhalation routes to carbon-14-labeled methylphosphonic difluoride (difluoro) or its hydrolysis products. Exposed rats were serially killed and dissected so that the movement of the radiolabel could be traced over 7 days. Hydrolysis products cleared rapidly after noninhalation administration (t 1/2 less than 24 hr). The deposition of inhaled difluoro was mainly in the maxillo- and ethmoturbinates, and clearance was mainly by mucociliary clearance and swallowing. Constants were calculated for relating doses of difluoro to various respiratory tract tissues as a function of total deposited vapor. These constants indicate that the maxilloturbinates in the anterior of the nose receive more than four times the dose of difluoro than do the ethmoturbinates, whereas the trachea and lung receive much lower doses than do the nasal tissues. The derived constants may be applicable for calculating doses to respiratory tract tissues for other inhaled vapors that do not saturate the mucus (e.g., irreversibly react with water).
mesh_terms: D000818:Animals; D001273:Atmosphere Exposure Chambers; D004064:Digestive System / Q000378:metabolism*; D005243:Feces / Q000032:analysis; D005260:Female; D006868:Hydrolysis; D008657:Metabolic Clearance Rate; D009943:Organophosphorus Compounds / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D012137:Respiratory System / Q000378:metabolism; D014018:Tissue Distribution; D014867:Water
chemical_list: D009943:Organophosphorus Compounds; D014867:Water; C046675:methylphosphonic difluoride