| Objective: To study the effect of limb ischemia preconditioning(LIP)on exercise duration and limit in exhausted exercise model of continue swimming in rats, and explored the possible mechanism of antioxidant and peroxidation in it.Materials & Methods: 84 male SD rats were divided randomly into three groups: Group C(control group, n=12): No treatrment after inhalation of 2% sevoflurane for 30 min.; Group E(exhausted exercise group, n=36): revived naturally 24 h after inhalation of 2% sevoflurane for 30 min and loaded with 5% of their body weight, subjected to exhausting swimming; and Group LE(limb ischemia preconditioning group and exhausted exercise group, n=36): During 30 min of inhalation of 2% sevoflurane, the bloodflow of the root of right hindlimb was blocked by tourniquet for 5min, followed by reperfusion of 5min for 3 circles to establish LIP. 24 h after natural revival, they were treated in the same way as Group E. The Group E and Group LE were randomly divided into sub-groups:(E1, E2, E3 and LE1, LE2, LE3,respectively, n=12), subjected to one-hour, two-hour and exhausting swimming. The exhausting swimming duration of those two groups were observed, and the blood samples of them were taken from their eyeballs. Immediately after acute exhausting exercise, the levels of Superoxide Dismutase(SOD), Malondialdehyde(MDA), Creatine Kinase(CK), Lactic acid(LAC)and Lactate Dehydrogenase(LDH)in skeletal muscle were determined by xanthine oxidase assay, thiobarbituric acid assay, creatine kinase colorimetric assay, lactate oxidase assay and chromatometry respectively. The degrees of muscle injury of the gastrocnemius muscles of right hindlimb were observed under light microscope after HE staining and pathological analysis.Results: ① The exhausting models of continuing swimming and LIP have been successfully established; ②The exhausting exercise time limit in Group LE was longer than that in Group E, the range of increase was 17.97%(p<0.05); ③The SOD and the ratios of SOD/MDA in different groups were as follows: Group LE >Group C > GroupE. The swimming time extended, Group LE and Group E were on the rise. After Swimming 1h, the comparison between two subgroups were statistically significant(p<0.05); ④The MDA are Group E>Group LE> Group C. Time extended, Group LE and Group E are on the rise. After swimming 1h, the comparison between two subgroups was statistically significant(p<0.05); ⑤The trends of CK in Group LE and Group E were similar as that of MDA.; ⑥ The LAC are Group E>LE group>Group C. The swimming time extended, Group LE and Group E were on the rise. After Swimming 2h, the comparison between two subgroups was statistically significant(p<0.05); ⑦ The LDH were Group LE >Group E>Group C. Time extended, Group LE and Group E were on a declining curve. The pairwise comparison between two subgroups was not statistically significant(p>0.05); ⑧The pathological changes of musculus gastronomies were founded that muscle fibers of Group E had been slightly transformed after swimming1 h, parts of them had been broken, but the myolemma of them was still distinct. The swimming time extended, the muscle fibers were transformed, the damage worsen and the myolemma not distinct. Inflammatory response and focal necrosis became more serious, inflammation cells were soaked, with Group E as the most distinct. The lesions in Group LE were lesser than those in Group E. Observed by light microscope, the scores of Group LE and Group E were remarkably higher than those of Group C. But the scores of Group LE were lower than those of Group E(p<0.05), which shows lesions of skeletal muscle in Group LE were lesser than those in Group E.Conclusions: ①The exhausting models of continuing swimming have been successfully established with rats loaded and swimming continuously; The muscles of rats were made ischemic for 5min, followed by reperfusion of 5min for 3 circles to establish LIP.②24h after treating with LIP, the exhausting exercise time limit can be extended, the exercise tolerance increased and the exhausting swimming time deferred. ③24h after treating with LIP, the cells damage of skeletal muscle due to exhausting exercise can be relieved. Time limit of swimming is 1h with the aim of protection.④The protective mechanism of LIP were set up mainly by increasing the animals’ antioxidant ability, eliminating oxygen radical, stabilizing functions of theenzymes in cells and decreasing the damages to cytomembrane by free radicals so as to alleviate the damage to skeletal muscle and relieve fatigue. |
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