Effect of Papain-Induced Emphysema on Canine Pulmonary Elastin

Abstract

Experimental emphysema was induced in 8 beagles by repeated administration of crude papain via aerosol and intratracheal instillation. Significant increases in mean linear intercept in the lungs of the papain treated dogs were consistent with morphological evidence of ruptured alveolar septa. The proportions of elastin in the parenchymal connective tissue were calculated from the desmosine and isodesmosine content of the total connective tissue and of purified elastin from the same specimens. Mean pulmonary elastin proportions determined 2 wk after the last dose of papain in 4 dogs with experimental emphysema were only 4.52% .+-. 1.84 whereas mean pulmonary elastin proportions in 4 control dogs were 14.42% .+-. 3.55. In 2 dogs sacrificed 3 mo. after the termination of the insult, mean pulmonary elastin proportions were not significantly different from those in the control dogs. Since the elastolytic activity of papain is very low, the elastin may be degraded in vivo by other mechanisms involving enhancement of endogenous elastase activity.