Abstract: Objective To investigate the protective effect of ulinastatin (UTI) against acute lung injury induced by heatstroke in
mice. Methods Sixty C57/BL6 mice were randomly divided into 6 groups, with 10 mice in each: control group, heatstroke
group, UTI pretreatment group, saline pretreatment group, UTI post-treatment group, saline post-treatment group. The
control mice were housed at a controlled room temperature of (22 ± 1) ℃ , and the other groups were placed inside a
temperature and humidity controlled chamber pre-set at 37 ℃ and 60%. The two UTI groups were intraperitoneally injected
with UTI at 5×104 U/kg 10 min before or after heat stress, and the two saline groups were given then equal amounts of saline in
the same manner. The core body temperature of mice was monitored by a mercury thermometer every 30 min in the first 1.5 h
during heating. The core temperature was measured, then every 15 min until it reached 42.7 ℃, which was taken as the onset
of heatstroke. The animals were allowed to recover passively at ambient temperature for 6 h. The lung histopathological
changes, protein concentration in BALF, lung wet/dry weight ratios, lung water content, and pulmonary microvascular
permeability were assayed after 6 h of recovery at 37 ℃. Results Compared with the control group, the heatstroke model
group and two saline groups displayed more severe lung damage and pathological morphology changes, and the lung wet/dry
weight ratio, protein concentration in BALF, lung water content and pulmonary microvascular permeability were also
significantly increased. These effects were significantly alleviated in UTI treated group. Pretreat ment with UTI significantly
prolonged the time to Tc≥42.7 ℃ but had no effect on lung injury induced by heatstroke. Conclusion UTI can reduce the
pulmonary edema and inflammatory exudation in acute lung injury caused by heatstroke.