title: The effect of assay conditions on the measurement of anti-elastase function in lung secretions.
abstract: We have determined the effect of altering assay conditions on the observed neutrophil elastase inhibitory capacity in lung secretions from emphysematous patients with normal serum alpha 1 PI. alpha 1 PI, ALP and alpha 2-macroglobulin were detected in all samples. Measurement at low enzyme concentration (less than 33.6 nmol/l) caused a 43% reduction in observed neutrophil elastase inhibitory capacity of sputum sol-phase, while inhibition by secretions in buffer without added NaCl was 20% greater than in the presence of 0.2 mol/l NaCl. Increasing the concentration of the synthetic substrate Suc-[Ala]3-pNA in the assay from 0.45 mmol/l to 7.2 mmol/l reduced the observed inhibitory capacity by 53% and the use of elastin-fluorescein gave lower results for inhibitory capacity than the Suc-[Ala]3-pNA (median 0.26 mol neutrophil elastase/mol measured inhibitors (range 0-0.72) with elastin; 1.40 mol neutrophil elastase/mol measured inhibitors (0.80-3.21) with Suc-[Ala]3-pNA). Assay conditions therefore greatly influence the results. In addition these findings suggest the presence of an additional inhibitor of neutrophil elastase in these secretions.
mesh_terms: D001991:Bronchitis / Q000201:enzymology; D002908:Chronic Disease; D004646:Emphysema / Q000201:enzymology; D006801:Humans; D008168:Lung / Q000378:metabolism* / Q000502:physiology; D008875:Middle Aged; D009504:Neutrophils / Q000201:enzymology; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors*; D013183:Sputum / Q000201:enzymology
chemical_list: D010196:Pancreatic Elastase