title: Micron-sized intrapulmonary particle deposition in the developing rat lung.
abstract: Little is known about the effects of postnatal developmental changes in lung architecture and breathing patterns on intrapulmonary particle deposition. We measured deposition in the developing Wistar-Kyoto rat, whose lung development largely parallels that of humans. Deposition of 2-μm sebacate particles was determined in anesthetized, intubated, spontaneously breathing rats on postnatal days (P) 7 to 90 by aerosol photometry (Karrasch S, Eder G, Bolle I, Tsuda A, Schulz H. J Appl Physiol 107: 1293-1299, 2009). Respiratory parameters were determined by body plethysmography. Tidal volume increased substantially from P7 (0.19 ml) to P90 (2.1 ml) while respiratory rate declined from 182 to 107/min. Breath-specific deposition was lowest (9%) at P7 and P90 and markedly higher at P35 (almost 16%). Structural changes of the alveolar region include a ninefold increase in surface area (Bolle I, Eder G, Takenaka S, Ganguly K, Karrasch S, Zeller C, Neuner M, Kreyling WG, Tsuda A, Schulz H. J Appl Physiol 104: 1167-1176, 2008). Particle deposition per unit of time and surface area peaked at P35 and showed a minimum at P90. At an inhaled particle number concentration of 10(5)/cm(3), there was an estimated 450, 690, and 330 particles/(min × cm(2)) at P7, P35, and P90, respectively. Multiple regression models showed that deposition depends on the mean linear intercept as structural component and the breathing parameters, tidal volume, and respiratory rate (r(2) > 0.9). In conclusion, micron-sized particle deposition was dependent on the stage of postnatal lung development. A maximum was observed during late alveolarization (P35), which corresponds to human lungs of about eight years of age. Children at this age may therefore be more susceptible to micron-sized airborne environmental health hazards.
authors.affiliation: Institute of Epidemiology I, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, D-85764 Neuherberg/Munich, Germany. schulz@helmholtz-muenchen.de
authors.forename: Holger
authors.initials: H
authors.lastname: Schulz
authors.forename: Gunter
authors.initials: G
authors.lastname: Eder
authors.forename: Ines
authors.initials: I
authors.lastname: Bolle
authors.forename: Akira
authors.initials: A
authors.lastname: Tsuda
authors.forename: Stefan
authors.initials: S
authors.lastname: Karrasch
mesh_terms: D000336:Aerosols / Q000032:analysis / Q000378:metabolism; D000818:Animals; D005260:Female; D008168:Lung / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D010316:Particle Size; D010783:Photometry / Q000379:methods; D051381:Rats; D011921:Rats, Inbred WKY; D012044:Regression Analysis; D056152:Respiratory Rate / Q000502:physiology; D013990:Tidal Volume / Q000502:physiology
chemical_list: D000336:Aerosols