Meir Jessica U, Ponganis Paul J
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA.
J Exp Biol. 2009 Oct;212(Pt 20):3330-8. doi: 10.1242/jeb.033761.
The emperor penguin (Aptenodytes forsteri) thrives in the Antarctic underwater environment, diving to depths greater than 500 m and for durations longer than 23 min. To examine mechanisms underlying the exceptional diving ability of this species and further describe blood oxygen (O2) transport and depletion while diving, we characterized the O2-hemoglobin (Hb) dissociation curve of the emperor penguin in whole blood. This allowed us to (1) investigate the biochemical adaptation of Hb in this species, and (2) address blood O2 depletion during diving, by applying the dissociation curve to previously collected partial pressure of O2 (PO2) profiles to estimate in vivo Hb saturation (SO2) changes during dives. This investigation revealed enhanced Hb-O2 affinity (P50=28 mmHg, pH 7.5) in the emperor penguin, similar to high-altitude birds and other penguin species. This allows for increased O2 at low blood PO2 levels during diving and more complete depletion of the respiratory O2 store. SO2 profiles during diving demonstrated that arterial SO2 levels are maintained near 100% throughout much of the dive, not decreasing significantly until the final ascent phase. End-of-dive venous SO2 values were widely distributed and optimization of the venous blood O2 store resulted from arterialization and near complete depletion of venous blood O2 during longer dives. The estimated contribution of the blood O2 store to diving metabolic rate was low and highly variable. This pattern is due, in part, to the influx of O2 from the lungs into the blood during diving, and variable rates of tissue O2 uptake.
帝企鹅（Aptenodytes forsteri）在南极水下环境中繁衍生息，能潜至超过500米的深度，潜水时长超过23分钟。为研究该物种卓越潜水能力背后的机制，并进一步描述潜水时血液中氧气（O₂）的运输和消耗情况，我们对帝企鹅全血中的O₂ - 血红蛋白（Hb）解离曲线进行了表征。这使我们能够：（1）研究该物种Hb的生化适应性；（2）通过将解离曲线应用于先前收集的O₂分压（PO₂）剖面，以估计潜水过程中体内Hb饱和度（SO₂）的变化，从而探讨潜水时血液O₂的消耗情况。这项研究揭示了帝企鹅具有增强的Hb - O₂亲和力（P50 = 28 mmHg，pH 7.5），这与高山鸟类和其他企鹅物种相似。这使得潜水时在低血液PO₂水平下能够增加O₂含量，并更完全地耗尽呼吸O₂储备。潜水过程中的SO₂剖面表明，在潜水的大部分时间里，动脉SO₂水平保持在接近100%，直到最后上升阶段才会显著下降。潜水结束时静脉SO₂值分布广泛，在较长时间的潜水中，静脉血O₂储备的优化源于静脉血O₂的动脉化和近乎完全耗尽。血液O₂储备对潜水代谢率的估计贡献较低且变化很大。这种模式部分归因于潜水时O₂从肺部流入血液，以及组织O₂摄取速率的变化。
