Study on the pathological changes of the lung and brain in mice during heat stress

Abstract

Objective To prepare mouse model with heat stress and determine its pathological changes of the lung and brain during heat stress. Methods BALB/c mouse were randomly (random number) divided into two groups, control group and heat stress group. The animals in the control group were sham- heated at a temperature of ( 25 ± 0.5) ℃ and humidity of (35 ± 5 ) %. The animals of heat stress group were placed in a prewarmed incubator maintained at (35.5 ± 0.5) ℃ and relative humidity of (60 ± 5) %. Rectal temperature (Tc) was monitored, and when Tc respectively reached 39 ℃, 40 ℃ , 41 ℃ and 42 ℃, those study animals were killed. The other animals were removed from the incubator and allowed to cool at an ambient temperature of (25 ±0. 5)℃ and humidity of (35 ±5)% , respectirvely for 12 and 24 hrs when Tc reached 41 ℃ , and for 6 hrs when Tc reached 42 ℃. The lung and brain of all the animals were isolated. Hematoxylin and eosin stain and light microscope were used to detect their pathological changes. Results All the animals displayed uniform response to the heat stress. Low degree of heat stress could induced obviously pathological changes of the lung, progressively greater damage to lung with further congestion of lung matrix, asystematic hemorrhage of alveolar space, abscission of alveolar epithelial cell and disappear of pulmonary alveolus tissue structure were detected with the rise of Tc to 42 ℃. However, absorption of congestion and hemorrhage and recovery of pulmonary alveolus tissue structure could also be seen with cooling at ambient temperature. With low degree of heat stress, the brain only showed moderate edema. Neuronal denaturation and necrosis were detected when Tc reached to 42 ℃. Interestingly, the lesions of brain further aggravated even through cooling treatment after Tc reached to 42 ℃ , but recovery could been observed after cooling treatment followed with Tc of 41 ℃. Conclusions The pathological changes of the lung and brain showed distinctive lesions to heat stress and cooling treatment, and these changes were correlated with the timing and time of cooling treatment, which provide the experimental basis to further study the mechanisms between the heatstroke and multiple organ dysfunction syndrome (MODS). Key words: Heat stress; Heatstroke; Lung; Brain; Pathological change; Mice; MODS; Cooling treatment