Exercises in Hot and Humid Environment Caused Liver Injury in a Rat Model

OBJECTIVE To investigate injury pattern during intense exercises in hot and humid environment particularly on liver in a rat exertional heat stroke model. METHODS We randomly divided 30 rats into a control group (CG), a normal temperature (25±2°C, 60%±5% humidity) exercise group (NTEG) and a high temperature and high humidity (35±2°C, 80%±10% humidity) exercising group (HTEG), each comprising 10 animals. The NTEG and HTEG rats were forced to run in a treadmill for 1 hour maximum at 20 rpm. We analyzed liver cells of all three groups with JC-1 dye and flow cytometry for apoptosis rates in addition to liver tissue 8 - hydroxy deoxyguanosine (8 - OhdG) and blood serum IL-6, tumor necrosis factor alpha (TNF-α), alanine aminotransferase ALT, aspartate amino transferase (AST), serum creatinine (CREA), blood urea nitrogen (BUN), lactate dehydrogenase (LDH), creatine phosphate kinase (CK) concentrations. RESULT Compared with NTEG rats, beside reduced exercise tolerance (60±5 vs. 15±3 minutes) (p = 0.002) the 8-OhdG liver tissue concentrations were significantly higher (p = 0.040) in the HTEG rats. The HTEG developed more organ tissue damage and cellular fragmentations of liver cells. In both exercise groups TNF-α and IL-6 serum concentrations were enhanced significantly (p<0.001) being highest in the HTEG animals. Serum ALT, AST, LDH, CREA, BUN and CK concentrations were significantly enhance in both exercise groups. CONCLUSION In our exertional heat stroke rat model, we found tissue damage particularly in livers during exercises in hot and humid environment that was related to inflammation, oxidative stress and apoptosis.