Hyaluronate concentration in tracheal lavage fluid from clinically normal horses and horses with chronic obstructive...

To establish concentration of hyaluronate (HA) in tracheal lavage fluid from healthy horses and horses with chronic obstructive pulmonary disease (COPD). ANIMALS AND SAMPLES: Tracheal lavage fluid samples (n = 42) from 18 horses, 11 with COPD, and 7 control horses.

Clinical examination of the respiratory tract, tracheal lavage, and blood sample collection were performed on horses without clinical signs of respiratory tract disease and horses with clinical signs of COPD. In some horses, 1 to 5 repeated examinations were performed at 1-week intervals. Tracheal lavage fluid samples were analyzed for cell numbers, and urea concentration (made in parallel with serum samples to evaluate sample dilution effect); HA was determined by radiometric assay.

Mean (+/-SEM) HA concentration in tracheal lavage fluid samples was significantly (P = 0.005) higher in horses with COPD (1,880 [+/-309] micrograms/L), compared with that in control horses (256 [+/-72] micrograms/L). The increase in HA concentration in tracheal lavage fluid of COPD-affected horses was verified by repeated sample collection and analysis.

In horses with chronic respiratory tract inflammation such as COPD, tracheal lavage fluid HA concentration is about 7 times higher than reference values. High HA concentration in the tracheal or bronchoalveolar lavage fluid may reflect pathophysiologic changes in connective tissue around bronchi and bronchioli, leading to continuous increased production of HA in horses with advanced forms of COPD.

Determination of tracheal lavage fluid HA concentration may be used as a marker of chronic inflammatory changes in the COPD-affected lung.