朱瑞娟, 饶鑫峰, 魏登邦*, 王多伟, 魏莲, 孙生祯
为了探讨高原鼢鼠(Myospalax baileyi)和高原鼠兔(Ochotona curzoniae)在低氧环境下适应耐力性挖掘活动和快速奔跑的生理机制，本文比较研究了这两种高原动物肝脏中苹果酸天冬氨酸穿梭系统(malate-spartate shuttle system, MA)的功能差异。测定高原鼢鼠和高原鼠兔的肝脏体重比、肝细胞中线粒体参数和血清中乳酸含量，克隆细胞质型苹果酸脱氢酶(cytoplasmic malate dehydrogenase, MDH1)和线粒体型苹果酸脱氢酶(mitochondrial malate dehydrogenase, MDH2)基因的编码区以及谷氨酸天冬氨酸转运蛋白(aspartate glutamate carrier, AGC)和苹果酸-α-酮戊二酸转运蛋白(oxoglutarate malate carrier, OMC)基因的部分序列；应用real-time PCR测定肝脏中MDH1、MDH2、AGC和OMC mRNA的表达水平；应用酶学方法测定了MDH1和MDH2的酶活力。结果显示：(1)高原鼢鼠肝脏体重比极显著地高于高原鼠兔(P < 0.01)，肝细胞线粒体数目和表面积显著高于高原鼠兔(P < 0.05)；高原鼠兔血清乳酸含量极显著高于高原鼢鼠(P < 0.01)；(2)高原鼢鼠肝脏中MDH1 mRNA表达水平和酶活力均极显著高于高原鼠兔(P < 0.01)，高原鼢鼠肝脏中MDH2 mRNA表达水平极显著高于高原鼠兔(P < 0.01)，酶活力显著高于高原鼠兔(P < 0.05)；高原鼢鼠肝脏AGC mRNA表达量极显著高于高原鼠兔(P < 0.01)，OMC mRNA表达量无显著性差异 (P > 0.05)；(3)高原鼠兔肝脏中MDH1 mRNA表达水平和酶活力极显著低于MDH2 (P < 0.01)，高原鼢鼠肝脏中MDH1 mRNA表达水平极显著高于MDH2 (P < 0.01)，酶活力没有显著性差异(P > 0.05)。这些结果说明高原鼢鼠通过增强MA的穿梭能力提高了对耐力性挖掘活动能量的供应，而高原鼠兔通过增强肝脏糖异生的作用为短暂快速的运动提供能源物质，从而有效地将骨骼肌无氧糖酵解产生的乳酸转化为糖原，减少了对氧的依赖性。
[Functional difference of malate-aspartate shuttle system in liver between plateau zokor (Myospalax baileyi) and plateau pika (Ochotona curzoniae).] [Article in Chinese]
ZHU Rui-Juan, RAO Xin-Feng, WEI Deng-Bang*, WANG Duo-Wei, WEI Lian, SUN Sheng-Zhen
Department of Biology, Qinghai University, Xining 810016, China
To explore the adaptive mechanisms of plateau zokor (Myospalax baileyi) to the enduring digging activity in the hypoxic environment and of plateau pika (Ochotona curzoniae) to the sprint running activity, the functional differences of malate-aspartate shuttle system (MA) in liver of plateau zokor and plateau pika were studied. The ratio of liver weight to body weight, the parameters of mitochondria in hepatocyte and the contents of lactic acid in serum were measured; the open reading frame of cytoplasmic malate dehydrogenase (MDH1), mitochondrial malate dehydrogenase (MDH2), and the partial sequence of aspartate glutamate carrier (AGC) and oxoglutarate malate carrier (OMC) genes were cloned and sequenced; MDH1, MDH2, AGC and OMC mRNA levels were determined by real-time PCR; the specific activities of MDH1 and MDH2 in liver of plateau zokor and plateau pika were measured using enzymatic methods. The results showed that, (1) the ratio of liver weight to body weight, the number and the specific surface of mitochondria in hepatocyte of plateau zokor were markedly higher than those of plateau pika (P < 0.01 or P < 0.05), but the content of lactic acid in serum of plateau pika was significantly higher than that of plateau zokor (P < 0.01); (2) MDH1 and MDH2 mRNA levels as well as their enzymatic activities in liver of plateau zokor were significantly higher than those of plateau pika (P < 0.01 or 0.05), AGC mRNA level of the zokor was significantly higher than that of the pika (P < 0.01), while no difference was found at OMC mRNA level between them (P > 0.05); (3) mRNA level and enzymatic activity of MDH1 was significantly lower than those of MDH2 in the pika liver (P < 0.01), MDH1 mRNA level of plateau zokor was markedly higher than that of MDH2 (P < 0.01), but the activities had no difference between MDH1 and MDH2 in liver of the zokor (P > 0.05). These results indicate that the plateau zokor obtains ATP in the enduring digging activity by enhancing the function of MA, while plateau pika gets glycogen for their sprint running activity by increasing the process of gluconeogenesis. As a result, plateau pika converts the lactic acid quickly produced in their skeletal muscle by anaerobic glycolysis and reduces dependence on the oxygen.
通讯作者：魏登邦 E-mail: firstname.lastname@example.org
朱瑞娟, 饶鑫峰, 魏登邦, 王多伟, 魏莲, 孙生祯. 高原鼢鼠和高原鼠兔肝脏苹果酸天冬氨酸穿梭系统的功能差异[J]. 生理学报 2012; 64 (2): 177-186.
ZHU Rui-Juan, RAO Xin-Feng, WEI Deng-Bang, WANG Duo-Wei, WEI Lian, SUN Sheng-Zhen. [Functional difference of malate-aspartate shuttle system in liver between plateau zokor (Myospalax baileyi) and plateau pika (Ochotona curzoniae).] [Article in Chinese]. Acta Physiol Sin 2012; 64 (2): 177-186 (in Chinese with English abstract).