A model for emphysema was produced in Syrian hamsters by one intratracheal injection of 1 mg of purified papain in saline solution. Papain produced pulmonary edema and hemorrhage initially but after four days collagen was lost from alveolar walls. Departitioning of alveoli occurred despite normal synthesis of lecithin and, probably, increased synthesis of protein. Total lung protein, collagen, and elastin did not change. Alveolar basement membrance connective tissue, particularly collagen, was digested but repair was stimulated as judged from cellular changes and protein synthesis rates. Two interpretations are possible: either collagen is redistributed in alveoli by digestion and synthesis with loss of interstitial connective tissue or the collagen content in alveolar walls is so small a proportion of total lung collagen that its disappearance was not measured.
Kilburn KH, Dowell AR, Pratt PC. Morphological and Biochemical Assessment of Papain-Induced Emphysema. Arch Intern Med. 1971;127(5):884-890. doi:10.1001/archinte.1971.00310170092012