Effect of papain-induced emphysema on permeability of rat lung to drugs.

To investigate the effect of a papain-induced emphysema-like condition on pulmonary absorption of drugs, rats were exposed to either papain aerosol or distilled water aerosol (control) intermittently for 2 wk, and rates of drug absorption from damaged and control lungs were compared. To measure absorption rates, 0.1 ml of drug solution (0.1-10 mM) was administered through a tracheal cannula to anesthetized animals, and after various times lungs were assayed for unabsorbed compound. In absorption experiments with the lipoid-insoluble compounds, mannitol, p-aminohippuric acid, and procaine amide ethobromide, all three drugs were absorbed from the lungs about twice as rapidly in papain-treated rats as in control. In contrast, procaine amide, a relatively lipoid-soluble drug, was absorbed at the same rate in both control and papain-treated animals. The results suggest that papain-induced lung damage increases the porosity of the pulmonary epithelium.