Rezende Enrico L, Gomes Fernando R, Malisch Jessica L, Chappell Mark A, Garland Theodore
Integrative Ecology Group, Estación Biológica Doñana, CSIC, Apdo. 1056, E-41080 Seville, Spain.
J Appl Physiol (1985). 2006 Aug;101(2):477-85. doi: 10.1152/japplphysiol.00042.2006. Epub 2006 Apr 6.
We studied relations between maximal O2 consumption (VO2 max) during forced exercise and subordinate traits associated with blood O2 transport and cellular respiration in four lines of mice selectively bred for high voluntary wheel running (S lines) and their four nonselected control (C) lines. Previously, we reported VO2 max of 59 females at three Po2 (hypoxia = 14% O2, normoxia = 21%, hyperoxia = 30%). Here, we test the hypothesis that variation in VO2 max can be explained, in part, by hemoglobin concentration and Po2 necessary to obtain 50% O2 saturation of Hb (an estimate of Hb affinity for O2) of the blood as well as citrate synthase activity and myoglobin concentration of ventricles and gastrocnemius muscle. Statistical analyses controlled for body mass, compared S and C lines, and also considered effects of the mini-muscle phenotype (present only in S lines and resulting from a Mendelian recessive allele), which reduces hindlimb muscle mass while increasing muscle mass-specific aerobic capacity. Although S lines had higher VO2 max than C, subordinate traits showed no statistical differences when the presence of the mini-muscle phenotype was controlled. However, subordinate traits did account for some of the individual variation in VO2 max. Ventricle size was a positive predictor of VO2 max at all three Po2. Blood Hb concentration was a positive predictor of VO2 max in S lines but a negative predictor in C lines, indicating that the physiological underpinnings of VO2 max have been altered by selective breeding. Mice with the mini-muscle phenotype had enlarged ventricles, with higher mass-specific citrate synthase activity and myoglobin concentration, which may account for their higher VO2 max in hypoxia.
我们研究了在强迫运动期间最大耗氧量（VO2 max）与四种为高自愿性轮转跑步而选择性培育的小鼠品系（S系）及其四个非选择对照（C）系中与血液氧气运输和细胞呼吸相关的次要性状之间的关系。此前，我们报告了59只雌性小鼠在三种氧分压（低氧 = 14% O2，常氧 = 21%，高氧 = 30%）下的VO2 max。在这里，我们检验这样一个假设，即VO2 max的变化部分可以由血红蛋白浓度、使血红蛋白（Hb）达到50%氧饱和度所需的氧分压（对Hb与O2亲和力的一种估计）以及心室和腓肠肌的柠檬酸合酶活性和肌红蛋白浓度来解释。统计分析控制了体重，比较了S系和C系，并且还考虑了小肌肉表型（仅存在于S系中，由孟德尔隐性等位基因导致）的影响，该表型会减少后肢肌肉质量，同时增加肌肉质量特异性有氧能力。尽管S系的VO2 max高于C系，但在控制小肌肉表型的存在时，次要性状没有统计学差异。然而，次要性状确实解释了VO2 max的一些个体差异。在所有三种氧分压下，心室大小都是VO2 max的一个正向预测因子。血液Hb浓度在S系中是VO2 max的正向预测因子，但在C系中是负向预测因子，这表明选择性育种改变了VO2 max的生理基础。具有小肌肉表型的小鼠心室增大，具有更高的质量特异性柠檬酸合酶活性和肌红蛋白浓度，这可能解释了它们在低氧状态下较高的VO2 max。
