Functional levels of alpha 2-macroglobulin in plasma in relation to emphysema

In most studies, concentrations of alpha 2-macroglobulin are determined by immunological techniques. In this study, the amidolytic activity of porcine pancreatic elastase complexed with alpha 2-macroglobulin was measured using an elastase-specific substrate, succinyl-trialanyl-p-nitroanilide. The activities of plasmas from 47 emphysema cases were compared with 39 normal subjects. The age ranges of both groups were from 50 to 84 years. The mean activity of bound elastase in emphysema cases was 2.48 +/- 0.03 kU/l of plasma. The mean for normal subjects was 1.48 +/- 0.11 kU/l of plasma. The difference was very significant (2P less than 0.001). All except 2 of the emphysema cases had smoked. The same results were obtained when only people who had smoked for 25 years or more were included in the analysis. All the plasma samples of people included in the study were assayed by an immunological method for absolute level (in g/l) of alpha 1-proteinase inhibitor. The levels of alpha 1-proteinase inhibitor for all the persons studied fell within the normal range for MM-phenotypes (2 to 4 g/l).