Experimental emphysema was induced in Syrian hamsters by: (a) intratracheal mstillation of elastase; or (b) i.nhala tion of paparin. aerosob. Additional hamsters served as controls and were either instmed with a sterile salme solution or exposed to an aerosol of enzyme diluent. After 3 wk, treated and control groups were simultaneously exposed to an aerosol of relatively in.solube 137 Cs-labeled, heat-treated alumi.nosilicate particles with an aerodynamic diameter of 1.4 or 1.6 j.!m. The lung deposition of particles measured 3 hr after in.halation expO§11lfe was si.gnificantly lower in. hamsters exposed to elastase or papain (45% and 65%, respectively of the amounts deposited in control hamsters). The mean whole-body retention data for each group were fitted with three-component exponential equations. The first component, which represented early clearance and constituted 78% to 83% of the initial body burden in all groups, occurred rapidly with a half-time of 0.6 to 0.8 days, and probably represented particles deposited i.n the nasopharynx and ciliated airways. The second component represented an intermediate c:learance phase and was much faster in animals with emphysema than in controls. There were 6 and 11 day half-times in elastase- and papai.n-treated ham-sters, respectively, compared with 21 and 32 day haJJ-times in controls. The long-term clearance compQnent represented 4% and 5% of the mitial body burden i.n enzymetreated groups and 8% and 9% of the initial body burden i.n contrQI groups. The enzyme treatments resulted in a prolonged half-time m the long-term clearance component of 128 and 169 days compared to 98 and no days for the controls. The effect of both enzyme treatments on the retention of particles was similar althQugh the patterns of emphysema produced differed. Elastase instilled i.ntratracheally caused diffuse destructi.on and enlargement of alveoli with a loss of pulmonary elastic recoil. Papain aeJrOsols caused focal destruction and enlargement of alveoli arQund terminal bronchioles with no loss of elastic recoil. A common feature of both enzyme-treated groups was an increased number of alveQlar macmphages, which may account for the increased, early clearance Qf particles. The prolonged retention of a small fraction of particles may be due to focal accumulations Qf particle-bden macrophages which were prominent in distal alveoli Qf the papainexposed hamsters and, to a lesser degree, in the elastasetreated hamsters. © 1979 Taylor & Francis Group, LLC.
