Department of Biology, University of Ottawa, 30 Marie Curie Pvt, Ottawa, ON, K1N 6N5, Canada.
University of Ottawa Brain and Mind Research Institute, Ottawa, ON, Canada.
J Comp Physiol B. 2019 Apr;189(2):319-334. doi: 10.1007/s00360-019-01206-y. Epub 2019 Feb 6.
Damaraland and naked mole rats are the only eusocial mammalian species and live in densely populated, poorly ventilated underground burrows, within which they likely experience intermittent periods of hypoxia. Naked mole rats are the most hypoxia-tolerant mammal and do not exhibit a hypoxic ventilatory response to acute or chronic hypoxia but instead rely upon a robust hypoxic metabolic response to tolerate reduced environmental O. Conversely, physiological responses to hypoxia have not been explored in Damaraland mole rats but given their social and environmental similarities to naked mole rats, we hypothesized that they would exhibit similar physiological responses to hypoxia. We predicted that they would rely primarily on metabolic rate depression when O is limited and would not exhibit ventilatory responses to acute or chronic hypoxia. To test this hypothesis, we exposed Damaraland mole rats to normoxia (21% O) or progressive hypoxia (12-5% O), before and after acclimation to chronic hypoxia (8-10 days at 10% O), and measured ventilatory, metabolic, and thermoregulatory responses. We found that ventilation increased up to fourfold with progressive hypoxia and body temperature decreased ~ 2 °C; however, a hypoxic metabolic response was absent. Following acclimation to chronic hypoxia, ventilation in 21% O was ~ twofold higher than in control animals, indicating the occurrence of ventilatory plasticity to hypoxia, and body temperature and metabolic rate were elevated. However, ventilation was not further augmented in acute hypoxia following acclimation to chronic hypoxia, indicating that ventilatory acclimatization to hypoxia was atypical of other mammals. These results refute our hypothesis and we conclude that Damaraland and naked mole rats have divergent physiological responses to hypoxia.
达马拉兰鼹鼠和裸鼹鼠是仅有的两种真社会性哺乳动物物种，它们生活在人口密集、通风不良的地下洞穴中，在这些洞穴中，它们可能会间歇性地经历缺氧。裸鼹鼠是对缺氧最耐受的哺乳动物，它们不会对急性或慢性缺氧产生缺氧性通气反应，而是依靠强大的缺氧代谢反应来耐受环境中 O 的减少。相比之下，达马拉兰鼹鼠的生理对缺氧的反应尚未被探索，但考虑到它们与裸鼹鼠在社会和环境方面的相似性，我们假设它们会表现出相似的对缺氧的生理反应。我们预测它们在 O 有限时主要依赖代谢率降低，并且不会对急性或慢性缺氧产生通气反应。为了验证这一假设，我们在适应慢性缺氧（10% O 下 8-10 天）前后，将达马拉兰鼹鼠暴露在常氧（21% O）或逐渐缺氧（12-5% O）中，并测量通气、代谢和体温调节反应。我们发现，随着缺氧的加剧，通气量增加了四倍多，体温下降了约 2°C；然而，不存在缺氧代谢反应。在适应慢性缺氧后，21% O 下的通气量比对照动物高约两倍，表明存在对缺氧的通气可塑性，体温和代谢率升高。然而，在适应慢性缺氧后，急性缺氧时的通气量并没有进一步增加，表明对缺氧的通气适应与其他哺乳动物不同。这些结果反驳了我们的假设，我们得出结论，达马拉兰鼹鼠和裸鼹鼠对缺氧的生理反应不同。
