DOSE-DEPENDENT FATE OF ENZYMATICALLY ACTIVE AND INACTIVATED TRITIATED METHYLATED PANCREATIC ELASTASE ADMINISTERED INTRATRACHEALLY IN THE HAMSTER

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Abstract
Hamsters were intratracheally instilled with saline solutions containing a high dose (145-220 .mu.g) or a low dose (1.3-1.5 .mu.g) of 3H-methylated pancreatic elastase or N-acetyl-(L-alanyl)3 -L-alanine chloromethyl ketone-inactivated 3H-methylated pancreatic elastase. Only the lysyl residues of the elastase molecule were methylated and radiolabeled in a nonlabile manner. The 3H-methylated elastase preparation exhibited esterolytic and elastolytic activity, spectral properties, and emphysema-inducing properties indistinguishable from unmodified pancreatic elastase. There was no detectable hemorrhagic or emphysematous reaction with the inactivated 3H-methylated elastase, and this material was cleared from the lungs 11 .times. faster than the corresponding enzymatically active high dose of 3H-methylated elastase and 18 .times. faster than the corresponding enzymatically active low dose of 3H-methylated elastase. There were correspondingly higher amounts of radioactivity in the urine of hamsters treated with the inactivated elastase. All of the 3H radioactivity recovered from the urine was associated with .epsilon.-N-methyllysyl and .epsilon.-N,N-dimethyllysyl residues. Significant levels of radioactivity were found in the cells, primarily alveolar macrophages, lavaged from the lungs. The low dose of enzymatically active elastase caused neither detecable hemorrhage nor emphysema, both of which were associated with the high dose. At 144 days, significant radioactivity (1200 cpm) remained in the lungs of animals treated with high or low doses of enzymatically active elastase, whereas virtually no radioactivity (100 cpm) was found in the lungs of those treated with high or low doses of inactivated elastase. The data presented support the hypothesis that the formation of elastase complexes with .alpha.1-protease inhibitor and .alpha.2-macroglobulin is associated with the slower clearance and the retention of significant amounts of radioactivity in the lungs. Some of the residual radioactivity found in the hamster lungs may represent enzymatically active elastase complexed with .alpha.2-macroglobulin and may explain the progressive nature of emphysema induced by a single dose of elastase.