EQUININS IN EQUINE NEUTROPHILS - QUANTIFICATION IN TRACHEOBRONCHIAL SECRETIONS AS AN AID IN THE DIAGNOSIS OF CHRONIC PULMONARY-DISEASE

Equinins are a closely related group of proteins found in equine neutr ophil granules. They demonstrate proteinase inhibiting activity restri cted to microbial proteinase K and subtilisin, and they also possess a ntibacterial and antiviral properties. Antiproteinase K activity was m easured in tracheobronchial secretions (TBS) of horses with mild (n=15 ), moderate (n=30) and severe (n=16) chronic pulmonary disease, to det ermine its usefulness as an indicator of severity of disease and to me asure neutrophil content. Determination of proteinase K inhibiting act ivity was based on a colorimetric assay measuring the suppression of 4 -nitroaniline liberation from the synthetic substrate succinyl-L-alany l-alanyl-alanin-4-nitroanilid, a process mediated by proteinase K. Pro teinase K inhibiting activity proved to be a valid and simple indicato r for assessing neutrophil content in TBS and a useful parameter to de termine the severity of chronic pulmonary disease in the horse.