Williams Cassondra L, Sato Katsufumi, Shiomi Kozue, Ponganis Paul J
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, California 92093-0204, USA.
Physiol Biochem Zool. 2012 Mar-Apr;85(2):120-33. doi: 10.1086/664698. Epub 2012 Feb 29.
In diving birds and mammals, bradycardia and peripheral vasoconstriction potentially isolate muscle from the circulation. During complete ischemia, ATP production is dependent on the size of the myoglobin oxygen (O(2)) store and the concentrations of phosphocreatine (PCr) and glycogen (Gly). Therefore, we measured PCr and Gly concentrations in the primary underwater locomotory muscle of emperor penguin and modeled the depletion of muscle O(2) and those energy stores under conditions of complete ischemia and a previously determined muscle metabolic rate. We also analyzed stroke rate to assess muscle workload variation during dives and evaluate potential limitations on the model. Measured PCr and Gly concentrations, 20.8 and 54.6 mmol kg(-1), respectively, were similar to published values for nondiving animals. The model demonstrated that PCr and Gly provide a large anaerobic energy store, even for dives longer than 20 min. Stroke rate varied throughout the dive profile, indicating muscle workload was not constant during dives as was assumed in the model. The stroke rate during the first 30 s of dives increased with increased dive depth. In extremely long dives, lower overall stroke rates were observed. Although O(2) consumption and energy store depletion may vary during dives, the model demonstrated that PCr and Gly, even at concentrations typical of terrestrial birds and mammals, are a significant anaerobic energy store and can play an important role in the emperor penguin's ability to perform long dives.
在潜水鸟类和哺乳动物中，心动过缓和外周血管收缩可能会使肌肉与循环系统隔离开来。在完全缺血期间，ATP的产生取决于肌红蛋白氧（O₂）储备的大小以及磷酸肌酸（PCr）和糖原（Gly）的浓度。因此，我们测量了帝企鹅主要水下运动肌肉中的PCr和Gly浓度，并对完全缺血条件下以及先前确定的肌肉代谢率情况下肌肉O₂和这些能量储备的消耗进行了建模。我们还分析了划水频率，以评估潜水过程中肌肉工作量的变化，并评估该模型的潜在局限性。测得的PCr和Gly浓度分别为20.8和54.6 mmol kg⁻¹，与已发表的非潜水动物的值相似。该模型表明，即使对于超过20分钟的潜水，PCr和Gly也提供了大量的无氧能量储备。划水频率在整个潜水过程中有所变化，这表明潜水过程中肌肉工作量并非如模型所假设的那样恒定。潜水开始的前30秒内，划水频率随潜水深度的增加而增加。在极长的潜水中，观察到总体划水频率较低。尽管潜水过程中O₂消耗和能量储备的消耗可能会有所不同，但该模型表明，即使是陆地鸟类和哺乳动物典型浓度的PCr和Gly，也是重要的无氧能量储备，并且在帝企鹅进行长时间潜水的能力中可以发挥重要作用。
