低氧耐受对甘肃鼢鼠心肌的影响

【作者】 樊魏伟；

【导师】 何建平；

【作者基本信息】 陕西师范大学 ， 动物学， 2009， 硕士

【摘要】 甘肃鼢鼠(Myspalax cansus)隶属啮齿目(Rodentia),鼢鼠亚科(Myospalacinae),鼢鼠属(Myspalax),是我国黄土高原特有地下鼠,由于终生营地下洞穴生活,使得甘肃鼢鼠发展出良好的低氧耐受保护机制,本研究以甘肃鼢鼠和SD大白鼠(Sprague-Dawley)为对象,进行低氧耐受实验,探寻甘肃鼢鼠的低氧耐受极限,比较二者低氧耐受的差异;以及低氧耐受不同时程,二者心肌组织显微和超微结构的变化差异;比较分析左心室组织中HSP70的表达变化和心肌耐受过程中组织结构变化的相关性。研究结果表明:1.不同低氧梯度暴露,甘肃鼢鼠在3%,3.5%氧浓度,平均存活时长为1.03±0.14h和2.04±0.27h,SD大鼠分别是0.28±0.07h和0.48±0.08h。在4%氧浓度下甘肃鼢鼠可存活10小时以上,且行为状态良好,而SD大鼠仅存活4.87±0.45h。推测4%氧浓度可能是甘肃鼢鼠正常存活的低氧耐受极限。结果说明,严重低氧应激时,甘肃鼢鼠通过自身的应激保护机制,调动器官系统反应,及时调动对抗低氧的代偿机制,维持有氧代谢,保护内环境相对恒定,使其在4%氧浓度中逐渐适应,表现出很强的低氧耐受能力;SD大鼠在4%氧浓度大鼠暴露时,机体几乎没有能力和时间调动其代偿机制,仅存活4.87±0.45h,说明其无法对该低氧环境产生耐受。2.在4%氧浓度的低氧耐受实验中,甘肃鼢鼠在低氧2,4h后,心肌纤维收缩明显呈波浪状,低氧时间延长至6,8和10h后,心肌显微波浪状收缩由强逐渐变弱,并逐渐恢复至正常状态,说明鼢鼠心肌在6h以后对严重缺氧环境开始代偿性适应;SD大鼠2h组心肌纤维断裂严重,收缩加强成明显的波浪状,随着低氧时间得增加,4h组呈严重成挛状收缩,损伤加剧,提示SD大鼠在这一氧浓度下已经无法正常调动其代偿机制。3.在4%严重低氧耐受过程中,甘肃鼢鼠心肌超微结构在2h组出现血管扩张,通透性增加,有炎细胞渗出,异染色质边集;4h组心肌损伤状况与2h组接近,出现脂滴,提示脂类的氧化代谢在此时开始发生障碍,6和8h组心肌损伤状况逐渐好转,线粒体聚集增多,细胞连接正常,肌小节收缩较前有所减弱;10组线粒体增多聚集,线粒体脊增粗更为明显,少量糖原颗粒聚集,脂滴较前有所减少,横小管扩张增大变粗,出现了与能量代谢有关的结构适应性变化。证明了甘肃鼢鼠有强的低氧耐受能力,由于其心脏代偿能力比较强,减轻了缺氧引起的心肌损伤,心肌在低氧耐受过程中逐渐恢复。SD大鼠在2h心肌出现严重的超微病理损伤,4h组损伤加剧,说明4%浓度下大鼠没有能力调动其代偿机制,伴随心肌在短时间内的急剧损伤最终死亡。4.在4%氧浓度耐受不同时程后,HSP70在甘肃鼢鼠低氧各组左心室心肌组织中均广泛表达,与对照组比较差异极显著(P＜0.01),但各低氧相邻组间比较均无显著性差异(P＞0.05),HSP70的表达在2～4h极显著增加后到8～10h呈显著下降趋势(P＜0.05),而心肌超微结构状况在4h后也发生好转。提示HSP70蛋白表达增加,发挥细胞保护作用,使鼢鼠心肌细胞对低氧的耐受力增强,对该环境产生低氧耐受,处于逐渐适应的阶段。SD大鼠心肌在2,4h后HSP70蛋白大量表达,与对照组相比差异极显著(P＜0.01),但心肌终未见恢复,随后即发生死亡,说明HSP70在SD大鼠的极显著表达,还未能发挥其心肌保护作用,心肌未能恢复,SD大鼠即发生死亡。常氧对照组中甘肃鼢鼠HSP70的表达量明显高于SD大鼠(P＜0.01),可能是甘肃鼢鼠应对极端低氧环境时心肌自身保护特有的机制。甘肃鼢鼠在低氧2,4h的HSP70表达是极显著高于SD大鼠(p＜0.01),但其表达增长幅度分析,二者间不存在显著性差异(P＞0.05)。说明该应激蛋白在二者心肌中有相似的低氧应激反应,但HSP70在鼢鼠各组都极显著高于SD大鼠,这可能促使鼢鼠机体和心脏有更强的低氧耐受力,HSP70大量表达使得鼢鼠心肌细胞对缺氧的耐受也显著强于SD大鼠,使其在低氧损伤心肌中发挥了强的保护作用,鼢鼠心肌逐渐恢复。说明甘肃鼢鼠在该浓度下心肌得低氧耐受能力明显强于大鼠。综上所述,本研究结果说明甘肃鼢鼠虽长期生活在地下低氧环境中,但对严重的低氧环境仍比较敏感,在一定程度的严重低氧刺激下才会迫使其顺利启动其自身从分子、细胞水平到整体协调的低氧耐受机制,使心脏不至出现衰竭的现象,从而在心肌组织结构稳定的情况下,发挥正常功能,维持在低氧条件下的生存。更多还原

【Abstract】 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.更多还原