高原鼢鼠和高原鼠兔心脏对低氧环境的适应

Hypoxic adaptation of the hearts of plateau zokor (Myospalax baileyi) and plateau pika (Ochotona curzoniae)

为了探讨高原鼢鼠和高原鼠兔心脏对低氧环境的适应机制,以Sprague-Dawley(SD)大鼠为对照,测量三者的心脏/体重比(HW/BW)、右心室/(左心室+室间隔)重量比[RV/(LV+S)];应用免疫组织化学方法测定心肌微血管密度(microvessel density,MVD);通过显微体视学技术比较线粒体的面数密度(NA,单位面积中线粒体数目)、体密度(VV,单位体积心肌纤维中线粒体的体积密度)、面密度(SV,单位体积心肌纤维中线粒体外膜的面积密度)、比表面(δ,线粒体外膜面积与其自身体积的比);用分光光度法测定心肌中的肌红蛋白(myoglobin,Mb)含量、乳酸(lactic acid,LD)含量和乳酸脱氢酶(lactate dehydrogenase,LDH)活力;聚丙烯酰胺凝胶电泳观察LDH同工酶谱。结果显示:高原鼢鼠和高原鼠兔HB/WB显著大于SD大鼠(P<0.05),RV/(LV+S)显著小于SD大鼠(P<0.05)。高原鼢鼠、高原鼠兔和SD大鼠心肌MVD和线粒体NA依次递减(P<0.05);高原鼢鼠线粒体VV显著低于高原鼠兔和SD大鼠(P<0.05),高原鼠兔与SD大鼠之间没有明显差异;高原鼢鼠线粒体SV显著高于SD大鼠(P<0.05),与高原鼠兔相比无明显差异;高原鼠兔和SD大鼠的线粒体δ无显著差异,但均明显低于高原鼢鼠(P<0.05)。高原鼢鼠和高原鼠兔心肌Mb含量显著高于SD大鼠(P<0.05);高原鼢鼠心肌LD含量显著高于高原鼠兔和SD大鼠(P<0.05);两种高原动物心肌LDH活力显著低于SD大鼠(P<0.05)。同工酶谱显示,高原鼢鼠、高原鼠兔和SD大鼠的LDH中H亚基所占比例依次递减。以上结果提示,高原鼢鼠和高原鼠兔通过增加心肌线粒体SV、MVD以及Mb含量提高其在低氧环境获取氧的能力;同时,由于生境和习性上的不同,两者线粒体指标又表现出差异性。

Plateau zokor （Myospalax baileyi） and plateau pika （Ochotona curzniae） are native to the Qinghai-Tibet plateau. To study their adaptive mechanisms, the ratios of heart weight to body weight （HW/BW） and right to left ventricular plus septum weights [RV/（LV＋S）] were determined; the microvessel density （MVD） of cardiac muscle were measured by immunohistochemical staining; the numerical density on area （NA）, volume density （Vv）, specific surface （δ）, and surface density （Sv） of mitochondria were obtained by microscopy and stereology; the contents of myoglobin （Mb） and lactic acid （LD）, and the activity of lactate dehydrogenase （LDH） in cardiac muscle were analyzed by spectrophotometer. The results showed that the HW/BW of plateau zokor [（4.55±0.26）%] and plateau pika [（4.41±0.38）%] was significantly greater than that of Sprague-Dawley （SD） rat [（3.44±0.41）%] （P〈0.05）, but the RV/ （LV＋S） [（22.04±1.98）%, （25.53±3.41）%] was smaller than that of SD rats [（44.23±3.87）%] （P〈0.05）. The MVD and NA of cardiac muscle were 1688.631±250.253 and 0.768±0.123 in SD rat, 2002.888±367.466 and 0.868±0.159 in plateau pika and 2990.643±389.888 and 1.012±0.133 in plateau zokor. The Vv of mitochondria in plateau zokor （0.272±0.045） was significantly lower than that in plateau pika （0.343±0.039） and SD rat （0.321±0.048） （P〈0.05）, while the δ of mitochondria in plateau zokor （9.409±1.238） was higher than that in plateau pika （6.772±0.892） and SD rat （7.287± 1.373） （P〈0.05）. The Sv of mitochondria in plateau pika （2.322±0.347） was not obviously different from that in plateau zokor （2.468±0.380） and SD rat （2.227±0.377）, but that in plateau zokor was significantly higher than that in SD rat （P〈0.05）. The contents of Mb in cardiac muscle of plateau zokor [（763.33±88.73） nmol/g] and plateau pika [（765.96±28.47） nmol/g] were significantly higher than that of SD rat [（492.38±72.14） nmol/g] （P〈0.05）, the content of LD in plateau zokor [（0.57±0.06）mmol/L] was obviously higher than that in plateau pika [（0.45±0.06）mmol/L] and SD rat [（0.48±0.02） mmol/L] （P〈0.05）, and the activity of LDH in plateau zokor [（16.90±2.00） U/mL] and plateau pika [（20.55±2.46） U/mL] were significantly lower than that in SD rat [（38.26±6.78） U/mL] （P〈0.05）. The percentage of LDH-H in cardiac muscle decreased in order in plateau zokor, plateau pika and SD rat. In conclusion, plateau zokor and plateau pika adapt better to hypoxia than SD rat by increasing the Sv of mitochondria, MVD and content of Mb in the cardiac muscle. However, the parameters of mitochondria in the two high-altitude animals are different possibly because of the differences of habitats and habits.