| Skeletal muscle is an important organization for movement system of mammalian, whose body movement is completed through the systole and diastolic of skeletal muscle. Gansu zokor is the unique specie of subterranean rodents in Loess Plateau, China, which lives under the ground all their life. To adapt the underground hypoxic environment, the structure and function of their body have come out many great changes. Through comparing the characteristics of skeletal muscle between Gansu zokor and SD rats under hypoxic conditions, would investigate the adaptation mechanism of Gansu zokor skeletal muscle under the hypoxia environment.The results are as follows:1. With morphologic methods, the differences of skeletal muscle between Gansu zokor and SD rats under different conditions (Normoxia, hypoxia 2 weeks, hypoxia 4 weeks)were compared. The results showed that the morphology of cansus skeletal muscle did not change significantly during the different time, the muscle fiber arranged orderly, muscle membrane completed and clear, muscle striations arrayed regular and straight in the same shape and size, the nuclear relative larger, muscle fiber cylindrical and arranged in order, cytoplasm uniform staining and the nuclear located under the muscle membrane.There is a significant difference on SD rats muscle morphology when the hypoxia conditions time prolonged. The muscle fiber was significantly atrophied under the hypoxia environment for 2 weeks, and the muscle fiber gap increased, more disordered structure, cytoplasm was uniform. After 4 weeks of hypoxia, skeletal muscle fiber breakdown as well as different in sized, muscle fiber structure was significant disorder, part of the areas appeared single muscle fiber rupture and sarcomere disorder, and cells closely arranged but not clearly, nuclear was scattered but chromatin condensed and closed to the nuclear membrane.It suggests that it is great important to study the normal skeletal muscle structure and function of cansus for their speciall physiological characteristics adapting hypoxic environment.2. The skeletal muscle lactate dehydrogenase (LDH) activity was measured between Gansu zokor and SD rat in normoxia and hypoxia 2 weeks, hypoxia 4 weeks, by UV spectrophotometer. The results showed that in normoxia between male and female cansus of the forelimbs and hindlimbs the LDH activity was not significantly different (P>0.05), the LDH activity was extremely significantly different (P<0.01) between the forelimbs and hindlimbs, and the LDH activity of forelimbs was significantly higher than the hindlimbs (P<0.05). After treatment with hypoxia for 2 weeks and 4 weeks, LDH activity decreased, but the difference was not significant (P> 0.05). After the SD rats treatment with hypoxia for 2 weeks, LDH activity increased, but the comparison with normoxia there was no significant difference (P> 0.05). It showed that the skeletal muscle metabolism of two different rodents lived in different environment showed different developmental trend in the process of hypoxia adaptation. Being adapted to tunnel life underground, forelimbs of Gansu zokor is used to dig and have more stronger anaerobic metabolism ability. Meanwhile, because of long life in the hypoxia environment underground, the LDH level was significantly lower than the SD rats, and after 2 weeks and 4 weeks under hypoxia, LDH levels did not change significantly. After the hypoxic adaptation for 2 weeks and 4 weeks LDH of SD rats will be increased, indicating the level of anaerobic metabolism rised.3. The skeletal muscle succinate dehydrogenase (SDH) activity was measured between Gansu zokor and SD rat in normoxia and hypoxia 2 weeks, hypoxia 4 weeks, with Using UV spectrophotometer. The results showed that under normoxic conditions, the SDH activity of forelimbs and hindlimbs of cansus was not significantly different (P> 0.05). After 2 weeks under hypoxia, SDH activities decreased and had no significant differences (P> 0.05) under normoxia. After 4 weeks under hypoxia, Gansu zokor SDH activity increased but no significant difference was showed among normoxia, hypoxia 2 weeks, and hypoxia 4 weeks (P> 0.05). After treatment under hypoxia for 2 weeks, SD rats SDH activity increased, but no significant difference by comparing with normoxia (P>0.05). After 4 weeks of hypoxic, SD rats SDH activity further increased but no significant difference by comparing with normoxia and hypoxia 2 weeks (P> 0.05). The study showed that two rodents skeletal muscle did not change significantly during aerobic metabolism in hypoxia.4. With UV spectrophotometer the skeletal muscle myoglobin (Mb) concentration was measured between Gansu zokor and SD rat in normoxia and hypoxia 2 weeks, hypoxia 4 weeks. The results showed that under normoxic conditions, Mb concentrations of forelimbs and hindlimbs of cansus were not significantly different (P> 0.05), the concentrations of forelimb between male and female were significantly different (P<0.01), and those of hindlimbs were no significant different (P> 0.05). After 2 weeks of hypoxia, Mb concentration was significant higher (P<0.01). After hypoxia for 4 weeks, Mb concentration decreased, showed highly significant differences by comparing with normoxia and hypoxia 2 weeks (P<0.01). The Mb concentration of forelimbs between male and female were significantly different (P<0.01), while those of hindlimbs have no significant difference (P> 0.05). After treatment under hypoxia for 2 weeks, SD rats Mb concentration decreased, but showed no significant difference (P>0.05) by comparing with normoxia. After hypoxia for 4 weeks, Mb concentration further decreased, but showed no significant difference (P>0.05) by comparing with normoxia and hypoxia 2 weeks. Mb concentration of forelimbs and hindlimbs of Myospalax cansus were higher than SD rats (P<0.05), and hypoxia for 2 and 4 weeks showed significantly higher than SD rats (P<0.01). The results indicated that Gansu zokor has special adapting mechanism for supplying oxygen to skeletal muscle, even in low oxygen environments during the movement.5 The body weight of normoxia and hypoxia 2 weeks, hypoxia 4 weeks of Gansu zokor and SD were measured. The results showed that body weight of cansus between male and female decreased during the hypoxia treatment, but there were no significantly different (P> 0.05) by comparing with normoxia. The body weight of both male and female SD rats decreased under hypoxia, but there were no significantly different (P> 0.05) by comparing with normoxia (P<0.01) and 2 weeks under hypoxia (P> 0.05). It suggested that Gansu zokor can quickly adapt the low oxygen environments in order to alter their own function to maintain the normal body weight.In conclusion, under the hypoxia environment, Gansu zokor and SD rats can use various organ systems and body regulation system to produce different adaptable mechanism in different levels, following that the enzymes activity of skeletal muscle for aerobic metabolism and anaerobic glycolysis were changed in order to complete body movement more effectively. Comparing with normoxia, the various indicators of skeletal muscle of Gansu zokor have no significant change and remain at a constant level. However, there were significant differences in the various indicators of SD rats when reaching a certain degree under the hypoxic stress. It indicates that Gansu zokor is insensitive to hypoxia stimulation because of living in the hypoxic environment for a long time. In the experiment they may start their own adaptation and coordination mechanism for hypoxic adaptation which makes each organ maintain stable to survive in such a hypoxic environment. |
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