| Skeletal muscle is an important organization in motor system of mammalian, and mammalian complete the body movement through contraction and relaxation of skeletal muscle. Gansu zokors (Myospalax cansus) is unique subterranean rodents of the Loess Plateau, life-long strictly living underground, and to adapt to low oxygen high carbon dioxide underground environment, the structure and function of skeletal muscle have taken place. This paper compared the structural and metabolic characteristics of groups between normoxia, acute and chronic hypoxia in SD and Gansu zokors, showing the adaptation mechanisms in Gansu zokors.The results are as follows:1. Through myosin-ATPase method compared gastrocnemius muscle fiber types and different types of muscle fiber cross-sectional area between SD and Gansu zokors of normoxia, acute hypoxia and chronic hypoxia treated groups, found after normoxia, acute hypoxia, chronic hypoxia treated gastrocnemius muscle fiber area of cansus did not change significantly, with the main muscle fiber typeⅡa, and few typeⅠ;an orderly arrangement of muscle fibers, clear boundaries, arranged in neat rows, form the same size in morphology.After acute hypoxia treated, gastrocnemius muscle fiber type and cross-sectional area of SD changed significantly,Ⅰtype muscle fiber ratio decreased slightly, but not significantly,Ⅱa type of muscle fiber cross sectional area increased significantly; after chronic hypoxia treated,Ⅰ-type muscle fiber ratio and muscle fiber cross-sectional area decreased significantly,Ⅱa type of muscle fiber ratio was significantly increased,Ⅱb type muscle fibers was significantly reduced, while cross-sectional area significantly increased. Morphology of chronic hypoxia showed SD rat gastrocnemius muscle fiber gap increased, its structure arranged disordered, and can be found fracture, broken, ill-defined, irregular shape, size inconsistent in some muscle fiber, muscle fiber structure was also disordered.All these showed that two different rodent living in different environment, skeletal muscle metabolism in hypoxic adaptation process showed different trends. cansus lived underground life-long, formed typeⅡa muscle fiber as a main type of muscle fibers, which is due to hypoxic conditions in long-term of mining activities needs. And there are a large number of typeⅠin SD gastrocnemius muscle fiber, indicated there was no hypoxic stress in the life of SD rats, and after treated with chronic hypoxia some muscle fibers break down, showed SD rats can not well adapted to hypoxia life.2. Through UV spectrophotometer method compared gastrocnemius muscle succinate dehydrogenase (SDH) activity between SD and cansus of normoxia, acute hypoxia and chronic hypoxia treated groups. The results showed that under normoxic conditions, male and female cansus SDH activity showed no significant difference (P> 0.05); under acute hypoxia treatment, cansus SDH activity decreased compared with normoxia, showed no significant difference (P> 0.05), there was no significant difference between male and female (P> 0.05);under chronic hypoxia treatment showed no significant difference compared with normoxia (P> 0.05), there was no significant difference between male and female (P> 0.05). The result of SDH activity of rat gastrocnemius muscle of SD rat showed that after acute hypoxia treatment, SDH activity increased compared with normoxia, showed a significant difference (P<0.05); after chronic hypoxia treatment, SDH activity increased further, compared with normoxia was significantly different (P<0.05)These illustrated living in two different environments, skeletal muscle metabolism in hypoxic adaptation process showed different trends. Cansus can adapt the underground tunnel life and SDH activity was not affected by environmental changes in oxygen concentration, can stable supply energy through aerobic metabolism. In contrast after acute and chronic hypoxia treated SDH activity of SD rats was significantly increased, indicating a dramatic increase in the level of aerobic metabolism.3 Through UV spectrophotometer method compared gastrocnemius muscle lactate dehydrogenase (LDH) activity between SD and cansus of normoxia, acute hypoxia and chronic hypoxia treated groups. The results showed that under normoxic conditions, between male and female LDH activity was not significantly different (P> 0.05); after acute hypoxia treatment, compared with normoxia, female cansus LDH activity was significantly decreased (P<0.05) while male cansus LDH activity was not significantly changed (P> 0.05); after chronic hypoxia treatment, compared with normoxia, the difference was not significant (P> 0.05). LDH activity in gastrocnemius muscle of SD rats showed that after acute hypoxia treatment, compared with normoxia, SD rats were significantly increased LDH activity (P<0.01); after chronic hypoxia treatment, compared with normoxia, SD rats were significantly increased LDH activity (P< 0.01).These illustrated living in two different environments, skeletal muscle metabolism in hypoxic adaptation process showed different trends. Cansus can adapt the underground tunnel life showed stronger anaerobic ability. At the same time, due to long-term adaptation to undergrounded life, the LDH levels were significantly higher than that of SD rats, and in acute and chronic hypoxia treatment, LDH levels did not change significantly; by contrast, SD rats in the acute, chronic hypoxia treatment groups LDH activity significantly increased, indicating a dramatic increase in the level of anaerobic metabolism.4 Through UV spectrophotometer method compared gastrocnemius myoglobin (Mb) concentration between SD and cansus of normoxia, acute hypoxia and chronic hypoxia treated groups. The results showed that under normoxic conditions, Mb between male and female of cansus showed no significant difference (P> 0.05); compared with normoxia, acute and chronic hypoxia treatment, cansus gastrocnemius muscle Mb concentration showed no significant difference (P> 0.05). Gastrocnemius Mb concentration of SD rats showed under normoxic conditions, compared with cansus, SD rats were significantly lower than cansus (P<0.01); after acute hypoxia, Mb concentration decreased, and significantly different from normoxia (P<0.05); after chronic hypoxia, Mb concentration further decreased compared with normoxia, showed significant difference (P <0.05). Gastrocnemius Mb concentration of cansus in normoxic, acute hypoxia, chronic hypoxia groups were significantly higher under the same conditions of SD rats (P<0.01). The result showed that skeletal muscle of cansus can supply adequate oxygen even in low oxygen environments can also meet the needs of skeletal muscle of oxygen.In a word, under hypoxic conditions all organ systems of Myospalax cansus and SD rats may produce different levels of adaptive changes, and gastrocnemius of aerobic and anaerobic glycolysis metabolic enzyme activity may change differently. After acute and chronic hypoxia conditions the parameters of cansus skeletal muscle have not significant changed compared with normoxic control group and remained at a constant level. While SD rats in the hypoxic stress when reached a certain degree changed significantly. All these showed that cansus living in underground environment of hypoxia was not sensitive to hypoxia, and they can successfully started their own mechanisms for overall coordination of the hypoxic adaptation, which keep various organs stability under low oxygen conditions to survival. |
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