A rapid procedure for the measurement of elastase inhibitory function of plasma and bronchoalveolar lavage fluid

Abstract

We describe a method to measure human leukocyte elastase (HLE) inhibitory capacity and compared it with porcine pancreatic elastase (PPE) inhibitory capacity and with a turbidimetric method using a specific antibody to alpha-1 antitrypsin (AAT), all performed on a Cobas Bio centrifugal analyser. This assay used methoxysuccinyl-dialanine-proline-valine-p-nitroanilide as substrate in the presence of 0.01% Brij 35, an HLE enzyme activator. Samples containing commonly used anti-coagulants and serum could be used in the assay, except for those containing heparin which strongly inhibited HLE. This assay was used to determine the functional AAT concentrations in plasma from a number of normal volunteers and patient groups, and was compared to the immuno-turbidimetric AAT assay. No difference in the proportion of functional to immuno-turbidimetric AAT was noted between any of the groups studied except for the adult respiratory distress syndrome (ARDS), where this percentage was reduced (p less than 0.05). An increase in both immuno-turbidimetric and functional AAT was seen for children (both p less than 0.01), in emphysema (p less than 0.05 and p less than 0.01 respectively) and ARDS (both p less than 0.05) when compared to adult non-smokers. This assay was also used to determine the HLE inhibitory capacity of serum and bronchoalveolar lavage (BAL) fluid from normal volunteer smokers (n = 4) and non-smokers (n = 4), and in the serum and BAL fluid from patients with ARDS (n = 5). Serum AAT was 94% functional in non-smokers (91% with PPE functional assay) and 96% in smokers (97% with PPE assay).(ABSTRACT TRUNCATED AT 250 WORDS)