Change in gastrocnemius dystrophin and metabolic enzymes and increase in high-speed exhaustive time induced by hypoxic training in rats

The aim of the present study was to explore the changes and roles of dystrophin and membrane permeability in hypoxic training. Seventy-two 8-week-old Sprague Dawley (SD) rats were randomly divided into 4 groups, normoxic non-train (NC), normoxic train (NT), hypoxic non-train (HC), and hypoxic train (HT) groups. The rats of each group were randomly divided into three subgroups, non-exhaustive, low-speed exhaustive test and high-speed exhaustive test subgroups. Rats in hypoxia groups lived and were trained in a condition of 12.7% oxygen concentration (equal to the 4 300 m altitude). NT and HT groups received 4 weeks of training exercise. Then the rats in all non-exhaustive subgroups were sacrificed, and gastrocnemii were sampled for the measurements of lactate dehydrogenase (LDH), succinatedehydrogenase (SDH), malate dehydrogenase (MDH) activities. Moreover, serum LDH activity was analyzed. Low-speed exhaustive test and high-speed exhaustive test subgroups received exhaustive tests with 20 (71% VO2max) and 30 m/min speed (86% VO2max), respectively, and their exhaustive times were recorded. The results showed that, compared with normoxic groups, the weights in hypoxia groups exhibited slower increase. The level of dystrophin in HT group without exhaustion test didn't change significantly. The muscle MDH activities were markedly affected by the different oxygen concentration, training and their interaction (P < 0.05), whereas the muscle LDH activities were only affected by the different oxygen concentration (P < 0.05). Serum LDH activities were affected by the interaction of the different oxygen concentration and training (P < 0.05), showing decreased muscle LDH and increased blood LDH activities. The exhaustion time were markedly affected by the different test speed, training and their interaction (P < 0.05), and also affected by the interaction of the different oxygen concentration and training (P < 0.05), but didn't affected by oxygen concentration. The exhaustive time of HT high-speed exhaustive test subgroup was more than NT high-speed exhaustive test subgroup in 30 m/min exhaustion test. Compared with NT high-speed exhaustive test subgroup, HT high-speed exhaustive test subgroup had an earlier fatigue in the test, but had a rapid recovery. These results suggested that hypoxic training can effectively increase the rats' high-speed exhaustive time. The mechanism may be related to an increase in serum LDH caused by the increased membrane permeability after hypoxic training.