Endothelin‐1 Concentrations in Bronchoalveolar Lavage Fluid of Cats with Experimentally Induced Asthma

Background There is a need for biomarkers for diagnosis, therapeutic monitoring, and prognosis for asthma in cats. Endothelin‐1 ( ET ‐1) is implicated in the pathogenesis of inflammatory airway diseases in other species but not the cat. Objective To conduct a prospective experimental study to show that experimentally asthmatic cats, but not control cats without airway inflammation, would have increased concentrations of ET in BALF . Animals Eleven healthy, adult research cats. Methods Prospective experimental study. Six healthy cats without airway inflammation were used as controls. Asthma was induced using Bermuda grass allergen ( BGA ) in 5 cats. Collection of BALF for total nucleated cell and differential counts was performed. The concentration of ET ‐1 in cell‐free BALF samples was determined. Data were analyzed using a M ann– W hitney U ‐test with P  < .05 considered significant. Results The median [range] BALF total cell numbers, eosinophil numbers, and eosinophil percentages were significantly higher in the cats following experimental induction of asthma (1,870 cells/μL [1,450–3,440], 711 cells/μL [356–1,686] and 38% [20–49]) compared to baseline control parameters (462 cells/μL [239–780], 18 cells/μL [18–62] and 3.5% [0–8]) ( P  < .01). The median [range] BALF ET concentration was also significantly higher after induction of asthma (1.393 fmol/mL[0.977–2.247]) compared to healthy control cats (0.83250 fmol/mL [0.625–1.038]) ( P  = .012). Conclusions and Clinical Importance This study suggests that BAL ET ‐1 concentration can be used to differentiate normal cats from those with experimentally induced asthma. If the same holds true for cats with naturally developing asthma, BAL ET ‐1 may prove a useful diagnostic biomarker for asthma.