Pulmonary inflammation due to exercise-induced pulmonary haemorrhage in Thoroughbred colts during race training

This study investigated the putative roles of inflammation and platelet-activating factor (PAF) in exercise-induced pulmonary haemorrhage (EIPH). Two-year-old Thoroughbred colts (n = 37) were exercised on a racetrack for 5 months before commencement of the study. Each colt was then exercised at 15–16 m/s over 800–1000 m and broncho-alveolar lavage fluid (BALF) was collected 24 h later. The colts were subsequently divided into two groups on the basis of BALF analysis; an EIPH-positive group (presence of haemosiderophages, n = 23) and an EIPH-negative group (absence of haemosiderophages, n = 14). BALF from the EIPH-positive group had a significantly higher protein concentration (0.39 ± 0.28 vs. 0.19 ± 0.12 mg/mL, P = 0.031), higher PAF bioactivity (0.18 ± 0.12 vs. 0.043 ± 0.05 340:380 nm ratio, P = 0.042) and a higher lipid hydroperoxide concentration compared to the EIPH-negative group. There was also a lower nitrite concentration and reduced production of superoxide anion and hydrogen peroxide by alveolar macrophages in the EIPH-positive group. There was evidence of pulmonary inflammation and a decreased innate immune response of alveolar macrophages in EIPH-positive colts compared with the EIPH-negative group.