HYALURONATE CONCENTRATION IN TRACHEAL LAVAGE FLUID FROM CLINICALLY NORMAL HORSES AND HORSES WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Objective-To establish concentration of hyaluronate (HA) in tracheal l avage fluid from healthy horses and horses with chronic obstructive pu lmonary disease (COPD). Animals and Samples-Tracheal lavage fluid samp les (n = 42) from 18 horses, 11 with COPD, and 7 control horses. Proce dure-Clinical examination of the respiratory tract, tracheal ravage, a nd blood sample collection were performed on horses without clinical s igns of respiratory tract disease and horses with clinical signs of CO PD. In some horses, 1 to 5 repeated examinations were performed at 1-w eek intervals. Tracheal ravage fluid samples were analyzed for cell nu mbers, and urea concentration (made in parallel with serum samples to evaluate sample dilution effect); HA was determined by radiometric ass ay. Results-Mean (+/- SEM) HA concentration in tracheal lavage fluid s amples was significantly (P = 0.005) higher in horses with COPD (1,880 [+/- 309] mu g/L), compared with that in control horses (256 [+/- 72] mu g/L). The increase in HA concentration in tracheal lavage fluid of COPD-affected horses was verified by repeated sample collection and a nalysis. Conclusions-In horses with chronic respiratory tract inflamma tion such as COPD, tracheal ravage fluid HA concentration is about 7 t imes higher than reference values. High HA concentration in the trache al or bronchoalveolar lavage fluid may reflect pathophysiologic change s in connective tissue around bronchi and bronchioli, leading to conti nuous increased production of HA in horses with advanced forms of COPD . Clinical Relevance-Determination of tracheal lavage fluid HA concent ration may be used as a marker of chronic inflammatory changes in the COPD-affected lung.