Fig. 3.
A: lower respiratory tract delivery/recovery of mouse granulocyte/macrophage colony-stimulating factor (GM-CSF) following aerosolization and administration of recombinant mouse GM-CSF (rmGM-CSF, 5 μg) to mice (n = 4–6 per group) over various exposure times and aerosol concentrations via the inExpose system. Immediately after aerosol exposure, bronchoalveolar lavage (BAL) fluid was recovered, and mouse GM-CSF levels were measured by ELISA. High-concentration aerosols with short exposure times (analyzed as a categorical variable) led to increased GM-CSF deposition in the lower respiratory tract compared with longer exposure times (*P < 0.05). B: analysis of exposure time as a continuous variable showed a significant negative correlation between exposure time and GM-CSF recovery. C: to assay the airway pharmacokinetics, aerosolized rmGM-CSF (5 μg, 100 μg/mL in PBS) was administered to mice (n = 5–6 per group) over 22.5 s, BAL fluid was recovered 0–4 h after exposure, and mouse GM-CSF levels were measured by ELISA. Airway pharmacokinetics of inhaled GM-CSF demonstrated a 2-compartment model with an initial (distribution) phase [half-life (t1/2) = 0.88 h] followed by a less-steep (terminal) phase (t1/2 = 1.3 h).