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, broncho alveolar lavage cytologic features and serum cortisol concentration, w ere 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/k g 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, maxi mal change in transpulmonary pressure (DELTAP(L)), pulmonary resistanc e (R(L)), and dynamic compliance (C(dyn)) were obtained during quiet b reathing, immediately before (baseline) and 1, 2, 3, 5, and 9 weeks af ter administration of TA. Pulmonary airway cells were collected by bro nchoalveolar lavage while horses were at pasture, at baseline, and 2, 5, and 9 weeks after TA administration. Serum cortisol concentration w as 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 immediate ly before and 30 minutes after administration of atropine (0.015 mg/kg , IV), to evaluate the reversibility of airway obstruction. In experim ent 1 at baseline, COPD-affected horses had significantly (P < 0.05) h igher values than did controls for f, DELTAP(L), R(L), and percentage of neutrophils, and had lower values for C(dyn) and percentage of lymp hocytes and macrophages. There were significant reductions in DELTAP(L ) and R(L), and increase in macrophage percentage after TA administrat ion in COPD-affected horses only. The degree and duration of these cha nges varied among individual COPD-affected horses, but DELTAP(L) and R (L) values had returned to or were above baseline in all horses 5 week s after treatment. Baseline cortisol concentration was decreased 4 wee ks after TA administration, but the mean increase in cortisol values a fter adrenocorticotropic hormone stimulation was similar to that obser ved prior to treatment. In experiment 2, values of DELTAP(L), R(L), an d C(dyn) after atropine administration were similar to those of contro ls in the 2 COPD-affected horses that had improved most after TA, but were only partially improved in the 3 other horses, indicating possibl e irreversible lesions in the latter.