Screening of evaluation indicators for motor skeletal muscle injury in rats in hot and dry desert environment

Objective To explore the histomorphology and related indicators in a rat model of skeletal muscle injury in an artificial experimental chamber as special environment in Northwest China to stimulate a hot and dry desert environment in order to screen the evaluation indicators of skeletal muscle injury in a hot and dry environment. Methods Eighteen male SD rats (8 weeks old) were randomly divided into blank control group (room temperature, free movement), room temperature exercise group, and hot and dry exercise group, with 6 rats in each group.After the rats were subjected to adaptation training for 3 d (a 3-D exercise treadmill, speed: 16 m/min, slope: -16°, time: 5~10 min), the rats in the 2 exercise groups were subjected to a treadmill once per day at a speed of 19.3 m/min and a slope of-16° till the end of exhaustion, and those in the hot and dry exercise group were housed in an artificial experimental chamber at a temperature of (40±1)℃, a humidity of (10±2)%.After 6 d of continuous exercise, the rat soleus muscle tissue was taken to observe the pathological changes, and the serum samples were detected for skeletal muscle injury markers, inflammatory factors, oxidative stress related factors, hormones and other related indicators. Results When compared with the blank control group and the room temperature exercise group, the hot and dry exercise group had significantly higher concentrations of creatine kinase (CK), creatine kinase isoenzyme (CK-MB) and myotype creatine kinase (CK-MM)(P < 0.05), elevated contents of TNF-α, IL-1β and IL-6(P < 0.05), raised malondialdehyde (MDA) content and lower superoxide dismutase (SOD) activity (P < 0.05), lower testosterone (T) but higher corticosterone (Cort) levels and thus lower testosterone/corticosterone (T/Cort) ratio (P < 0.05).The markers of skeletal muscle injury, CK, CK-MB and CK-MM were positively correlated with the pro-inflammatory cytokines, TNF-α, IL-1β and IL-6(P < 0.05), positively with the antioxidant indicator MDA but negatively with SOD (P < 0.05), and positively correlated with Cort level and negatively with T level and T/Cort ratio (P < 0.05). Conclusion A stable rat model of skeletal muscle injury in a hot and dry desert environment is successfully constructed.The severity of skeletal muscle injury is greater in rats in a hot and dry desert environment than those in a normal temperature environment.TNF-α and IL-1β are found to be indirect indicators to evaluate skeletal muscle injury in the environment.