Low Molecular Mass Bronchial Proteinase Inhibitor and α1-Proteinase Inhibitor in Sputum and Bronchoalveolar Lavage

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Abstract
The concentration of a low molecular mass bronchial mucus inhibitor of proteolytic enzymes (BMPI) was measured in lung secretions from patients with chronic bronchitis and compared to the concentrations of albumin and .alpha.1-proteinase inhibitor (.alpha.1-PI). The concentration of all 3 proteins was lower in bronchoalveolar lavage samples than in sputum obtained from the same patient. The relationship between the proteins (concentrations relative to each other) was similar in both secretions suggesting the differences in concentrations were only dilutional. The molar concentration of BMPI in both secretions was generally greater than that of .alpha.1-PI suggesting that most of the anti-elastase screen (.simeq. 75%) was due to the former protein. Inhibitory studies using both purified leukocyte elastase and porcine pancreatic elastase show that the inhibitory capacity of lung .alpha.1-PI varied and accounted for .apprx. 16% of the total inhibition of leukocyte elastase in sputum. The inhibitory function of .alpha.1-PI was less in bronchoalveolar lavage fluids compared to sputum (P < 0.05) and accounted for .apprx. 5% of the total inhibitory capacity for leukocyte elastase. .alpha.1-PI contributes only a part of the anti-elastase screen of secretions from patients with chronic bronchitis. It is inactivated to a varying degree in most secretions and its remaining inhibitory capacity represents only a minor proportion of the total inhibitory capacity.

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