| Myspalax cansus (Rodentia, Myospalacinae, Myspalax)which lives on the loess plateau of our country. This unique underground rats life-long living under the cave, it developed many hypoxic tolerance protect mechanism to adapt its special circumstances at in organsall levels. In this study,we used Gansu zokor and SD rats (Sprague-Dawley)for the object, do serious hypoxia tolerance experiment, to explore the hypoxia tolerance extreme of Gansu zokor, analysis the difference hypoxia tolerance between Gansu zokor and SD rats at same oxygen concentration; The changes on their cardiac muscle organization structures in hypoxia tolerance process ; The expression of HSP70 between normoxic and hypoxic control in cardiac muscle organization of two animals , to find the relativity in all the results. Trying to find the different hypoxia tolerance mechanisms between wild rats and mice , research shows that:1. In different levels extents of hypoxia experiments, Gansu zokors were surived 1.03±0.14h and 2.04±0.27h under 3.0%, 3.5% oxygen concentration respectively on average , the surive time of SD rats is 0.28±0.07h and 0.48±0.08h; Under 4% oxygen concentration , Gansu zokors can surive at least 10h, but SD rats just surived at this hypoixia extent for 4.87±0.45h on average. It can presumed 4% oxygen concentration is very close to Myspalax cansus hypoxia tolerance extreme.The results showing, in serious hypoxia stress, the resist hypoxia compensatory mechanism were mustered immediately and effectually in Gansu zokors by it's stress protect mechanism, organ and system reaction were transferred to keep aerobic metabolism and make the internal environment stable, then they can be tolerance and adapt to 4% oxygen concentration gradually, show its strong hypoxia tolerance ability. Under serious hypoxia environment , the compensatory mechanism in SD rats were not transferred in time , they were died about 4 hours later uder exposed to 4% oxygen concentration, the outcomes implied SD rats can not have tolerance to this hypoxia environment.2. 4% oxygen concentration were used as hypoxia tolerance research model., after 2 and 4h hypoxia that Gansu zokors cardiac muscle fibers were contracted to wavilness obviously under light microscope, but by the hypoxia time longer, cardiac muscle fibers were contracted weaked, the wavilness be lower in hypoxia 6h, 8h and 10h groups, the results show cardiac muscles has super compensatory mechanism and adapte to serious hypoxia stress. But in SD rats, cardiac muscle fibers were fractured seriouly , contracted to wavilness obviously, then muscle fibers fracture were contracted like entasia by the hypoxia time increased , injury intensify , all the changes refered SD rats compensatory mechanism can not be transferred in this hypoxia degree. 3. Exposed to 4% oxygen concentration, the cardiac muscle ultrastructure of Gansu zokors had serious injury after hypoxia 2h. angiectasis, permeability were increased , inflammatory cell were transuded; The cardiac muscle injury conditions after hypoxia 4 h were similar with hypoxia 2h group, appeared lipid droplet, implied the oxidative metabolism of lipid got obstacle started from then; The cardiac muscle injuried conditions were got little improvement in hypoxia 6 and 8 hours team, mitochondria were increased and aggregatived, normal cell junction, sarcomere contract weaked; in hypoxia 10h group , mitochondria were increased and aggregatived obviously, a few glycogenosome were assembled, transverse tubule were expanded, all the changes may be the adaption of Gansu zokors in the hypoxia tolerance process to 4% hypoxia extent gradually.The cardiac muscle ultrastructure of SD rats had seious pathology injury, in hypoxia 4h team,all the injury condition aggravated, the outcomes still show at 4% oxygen concentration,the compensatory mechanism can not be transfered, finally were died by cardiac muscle ultrastructure got grave injuried .4. HSP70 were expressed extensive in the cardiac muscle of Gansu zokors and SD rats after different hypoxia stress time. All the hypoxia groups , compared with normoxia group, there were very significant difference between them (P <0.01); in hypoxia 2,4h groups, there have no significant difference in Gansu zokors (P>0.05),and so as hypoxia 6 and 8h ,8 and 10h group; There were no sifnificant differerce between adjacency hypoxia teams(P>0.05).The extend of HSP70 expresslion were descend from 2-4h to 8-10h;In the same time, the cardiac muscle ultrastructure of Gansu zokors were be better, the results refered HSP70 were expressed extensive, its cell protection function were developed,made the cardiac muscle cells hypoxia tolerence be much stronger, It were persumed after 2-4h hypoxia , Gansu zokors were have tolerance to this circumstance from then on, and were got into the phases be adapive to the circumstance gradually.HSP70 were expressd extensive in the cardiac muscle compared with normoxia group in SD rats, after 2h and 4h hypoxia time, ,there were very significant difference between the two groups(P <0.01), but the cardiac muscle were not got resumed,, all of this lead to the faster died of SD rats, the results show the extensive erpression of HSP 70 in SD rats, its cell protection function were not developed , cardiac muscle were not got any resumed , the SD rats died.In the normal group,we find that HSP70 were expressed in Gansu zokors much more than in the SD rats, there were very significant difference between them (P <0.01), this is problely its owe mechanism of Gansu zokors cardiac muscle protection to resit the seirous hypoxia extend. In hypoxia 2.4h groups, HSP70 were expressed much more in Gansu zokors than in SD rats, there were very significant difference between them(P <0.01), but there were no significant difference on increase extend between them (P>0.05).It implied there were same hypoxia reaction of HSP70 in the two rats, but HSP70 were expressed much more in Gansu zokors than in SD rats, so it can be made Gansu zokors had strong hypoxia tolerance in body and cardiac muscle.In conclusion, the resuts suggests Gansu zokor long-term living in the underground environment of hypoxia,but still be sensitive to the serious hypoxia environment, just have different hypoxia tolerance limiting point. In the stimulation of grave hypoxia reach to one extent,Gansu zokor may impellingly smooth launch of its own mechanism to hypoxia from molecular, cellular and structure level to the overall coordination,and not to appeared heart failure. Gansu zokor will remain survival at the hypoxic conditions with the stability in cardiac muscle structure and its nomal function. |
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