Abstract:

Objective To screen the appropriate temperature and rewarming time of acute cold exposure （ACE） for establishing the rat model of myocardial injury induced by ACE， and to comprehensively evaluate the rationality and feasibility of the model establishment conditions through blood biochemistry， pathomorphology and molecular biology indicators. Methods Thirty male Wistar rats were randomly divided into -10 ℃， -15 ℃ and -20 ℃ cold exposure groups， with 10 rats in each group. The optimal modeling parameters （temperature and time） were determined by observing the mortality rates of the rats in various groups. Another fifty male Wistar rats were randomly divided into control group and rewarming （ACE/R） groups， which were further divided into 6/0， 6/6， 6/12 and 6/24 h groups according to rewarming time， with 10 rats in each group. The ACE/R model was established by cold exposure at -15 ℃ for 6 h followed by rewarming for corresponding time. The core body temperatures of the rats in various groups were detected， and the cardiac function of the rats in various groups was evaluated. HE staining was used to observe the pathological morphology of myocardium tissue of the rats in various groups； the serum levels of cardiac troponin I （cTnI） and the activities of aspartate aminotransferase （AST） and lactate dehydrogenase （LDH） of the rats in various groups were measured； enzyme-linked immunosorbent assay （ELISA） was used to detect the levels of interleukin-1β （IL-1β）， interleukin-18 （IL-18） and interleukin-6 （IL-6） in the myocardium tissue of the rats in various groups； real-time fluorescence quantitative PCR （RT-qPCR） was used to detect the expression levels of IL-1β， IL-18， IL-6 and tumor necrosis factor-α （TNF-α） mRNA in the myocardium tissue of the rats in various groups. Results Compared with control group， the core body temperatures of the rats in ACE/R groups at different time points were significantly decreased （P<0.05 or P<0.01）. Compared with control group， the left ventricular ejection fraction （LVEF） and left ventricular fractional shortening （LVFS） of the rats in 6/6， 6/12 and 6/24 groups were significantly decreased （P<0.05 or P<0.01）， and the left ventricular internal diameter in diastole （LVIDd） and left ventricular internal diameter in systole （LVIDs） of the rats in 6/12 group were significantly increased （P<0.05）. Compared with control group， the serum level of cTnI and the activities of AST and LDH of the rats in 6/12 group were significantly increased （P<0.01）. HE staining results showed that compared with control group， the myocardium tissue of the rats in 6/12 group showed disordered arrangement of myocardial fibers， widened intercellular spaces， and a large number of inflammatory cell infiltration. The ELISA results showed that compared with control group， the levels of IL-1β， IL-18 and IL-6 in the myocardium tissue of the rats in 6/12 group were significantly increased （P<0.01）. The RT-qPCR results showed that compared with control group， the expression levels of IL-1β， IL-18， IL-6 and TNF-α mRNA in the myocardium tissue of the rats in 6/12 group were significantly increased （P<0.05 or P<0.01）. Conclusion The ACE/R myocardial injury model can be established in the male Wistar rats by exposure of cold air at -15 ℃ for 6 h followed by rewarming at room temperature for 12 h.

Key words: Acute cold exposure, Myocardial injury, Rewarming, Wistar rats, Disease model， animal