Effects of triamcinolone acetonide on pulmonary function and bronchoalveolar lavage cytologic features in horses with chronic obstructive pulmonary disease.

Effects of triamcinolone acetonide (TA) on pulmonary function, bronchoalveolar lavage cytologic features and serum cortisol concentration, were studied in 5 control horses and 5 horses with chronic obstructive pulmonary disease (COPD). In experiment 1, horses were brought in from pasture 3 weeks before administration of 1 injection of TA (0.09 mg/kg of body weight, IM), and were stabled in dusty conditions throughout the experimental period. Measurements of respiratory rate (f), tidal volume, minute ventilation, expiratory-to-inspiratory time ratio, maximal change in transpulmonary pressure (delta PL), pulmonary resistance (RL), and dynamic compliance (Cdyn) were obtained during quiet breathing, immediately before (baseline) and 1, 2, 3, 5, and 9 weeks after administration of TA. Pulmonary airway cells were collected by bronchoalveolar lavage while horses were at pasture, at baseline, and 2, 5, and 9 weeks after TA administration. Serum cortisol concentration was measured before and after adrenocortical stimulation with 100 IU of adrenocorticotropic hormone, 1 week prior to TA administration, and 4 and 8 weeks thereafter. In experiment 2, 4 months after TA injection, pulmonary function measurements were repeated in all horses immediately before and 30 minutes after administration of atropine (0.015 mg/kg, IV), to evaluate the reversibility of airway obstruction. In experiment 1 at baseline, COPD-affected horses had significantly (P < 0.05) higher values than did controls for f, delta PL, RL, and percentage of neutrophils, and had lower values for Cdyn and percentage of lymphocytes and macrophages. There was significant reductions in delta PL and RL, and increase in macrophage percentage after TA administration in COPD-affected horses only.(ABSTRACT TRUNCATED AT 250 WORDS)