Pamenter Matthew E, Dzal Yvonne A, Milsom William K
Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
Proc Biol Sci. 2015 Feb 7;282(1800):20141722. doi: 10.1098/rspb.2014.1722.
Naked mole rats are the most hypoxia-tolerant mammals identified; however, the mechanisms underlying this tolerance are poorly understood. Using whole-animal plethysmography and open-flow respirometry, we examined the hypoxic metabolic response (HMR), hypoxic ventilatory response (HVR) and hypoxic thermal response in awake, freely behaving naked mole rats exposed to 7% O₂ for 1 h. Metabolic rate and ventilation each reversibly decreased 70% in hypoxia (from 39.6 ± 2.9 to 12.1 ± 0.3 ml O₂ min(-1) kg(-1), and 1412 ± 244 to 417 ± 62 ml min(-1) kg(-1), respectively; p < 0.05), whereas body temperature was unchanged and animals remained awake and active. Subcutaneous injection of the general adenosine receptor antagonist aminophylline (AMP; 100 mg kg(-1), in saline), but not control saline injections, prevented the HVR but had no effect on the HMR. As a result, AMP-treated naked mole rats exhibited extreme hyperventilation in hypoxia. These animals were also less tolerant to hypoxia, and in some cases hypoxia was lethal following AMP injection. We conclude that in naked mole rats (i) hypoxia tolerance is partially dependent on profound hypoxic metabolic and ventilatory responses, which are equal in magnitude but occur independently of thermal changes in hypoxia, and (ii) adenosine receptors mediate the HVR but not the HMR.
裸鼹鼠是已被鉴定出的最耐缺氧的哺乳动物；然而，这种耐受性背后的机制却知之甚少。我们使用全动物体积描记法和开放式流量呼吸测定法，研究了清醒、自由活动的裸鼹鼠在暴露于7%氧气环境1小时后的低氧代谢反应（HMR）、低氧通气反应（HVR）和低氧热反应。在低氧状态下，代谢率和通气量均可逆性降低70%（分别从39.6±2.9降至12.1±0.3毫升氧气·分钟⁻¹·千克⁻¹，以及从1412±244降至417±62毫升·分钟⁻¹·千克⁻¹；p<0.05），而体温未变，动物仍保持清醒和活跃。皮下注射通用的腺苷受体拮抗剂氨茶碱（AMP；100毫克·千克⁻¹，溶于生理盐水），而非对照生理盐水注射，可阻止HVR，但对HMR无影响。结果，经AMP处理的裸鼹鼠在低氧状态下表现出极度的过度通气。这些动物对低氧的耐受性也较低，在某些情况下，注射AMP后低氧会导致死亡。我们得出结论，对于裸鼹鼠而言，（i）耐缺氧能力部分依赖于深度的低氧代谢和通气反应，这两种反应程度相同，但在低氧状态下独立于热变化发生，并且（ii）腺苷受体介导HVR而非HMR。
