Automated measurement of the elastase-inhibitory capacity of plasma with a centrifugal analyzer.

We describe an automated method for measuring the elastase-inhibitory capacity of plasma. We use a GEMSAEC centrifugal analyzer and succinyltrialanine-p-nitroanilide as an elastase substrate. The method is fast (80--100 samples/h) and accurate (CV = 3.6%). The detection limits are from 20 to 300% of the normal value. The elastase-inhibitory capacity is well correlated with the trypsin-inhibitory capacity and with the immunochemically determined concentration of alpha 1-proteinase inhibitor (alpha 1-antitrypsin). Because elastase is not inhibited by other plasma inhibitors, this method can be used as an enzymatic technique for measuring the concentration of plasma alpha 1-proteinase inhibitor. In an apparently normal population, this concentration was 40 +/- 11 mumol/L.