Department of Animal and Biomedical Sciences, School of Life Science, Lanzhou University, Lanzhou, 730000, Gansu, China.
J Comp Physiol B. 2021 Nov;191(6):1019-1029. doi: 10.1007/s00360-021-01368-8. Epub 2021 Apr 19.
The Asiatic toad (Bufo gargarizans) belonging to the family of Bufonidae (Anura: Amphibia) is successfully residing on the Qinghai-Tibetan Plateau (QTP). To investigate whether the oxygen delivery undergoes adaptive adjustments to high-altitude environments in Asian toads inhabiting the QTP (Zoige County, 3446 m), choosing low-altitude populations (Chengdu City, 500 m) as control, we measured hematological traits, O affinities of whole blood, Hb-O affinities of purified Hbs, their sensitivities to temperature, and allosteric effectors (H, Cl and ATP). Our results showed that high-altitude Asiatic toads possessed significantly increased hemoglobin concentration, hematocrit, and red blood cell count, but significantly decreased erythrocyte volume compared with low-altitude toads. The whole blood and purified Hbs of high-altitude Asiatic toads both exhibited significantly higher O affinities compared with low-altitude toads. Substantially increased intrinsic Hb-O affinities of high-altitude Asiatic toads Hbs are likely to be the main reason for its elevated Hb-O affinities given the anionic cofactor sensitivities of high- and low-altitude toads were similar. The Hbs of high-altitude toads were also characterized by distinctly strong Bohr effects at the low temperature and low-temperature sensitivities. The adaptive adjustments of hematological traits could enhance the blood-O carrying capacity of high-altitude Asiatic toads. The increased Hb-O affinities could safeguard the pulmonary O uploading under hypoxia. The strong Bohr effects at the low temperature could help the release of O in metabolic tissues and cold limbs, while low-temperature sensitivity could minimize the effect of temperature fluctuation on the Hb-O affinity.
中华蟾蜍（Bufo gargarizans）隶属于蟾蜍科（Bufonidae）（无尾目：两栖纲），成功栖息于青藏高原（QTP）。为了研究在栖息于青藏高原（若尔盖县，3446 米）的亚洲蟾蜍中，氧气输送是否对高空环境进行了适应性调整，选择了低海拔种群（成都市，500 米）作为对照，我们测量了血液学特征、全血的 O 亲和力、纯化 Hbs 的 Hb-O 亲和力、它们对温度的敏感性和变构效应物（H、Cl 和 ATP）。结果表明，与低海拔蟾蜍相比，高海拔中华蟾蜍具有显著增加的血红蛋白浓度、血细胞比容和红细胞计数，但红细胞体积显著降低。高海拔中华蟾蜍的全血和纯化 Hbs 均表现出比低海拔蟾蜍更高的 O 亲和力。高海拔中华蟾蜍 Hbs 的内在 Hb-O 亲和力显著增加，可能是其 Hb-O 亲和力升高的主要原因，因为高海拔和低海拔蟾蜍的阴离子辅助因子敏感性相似。高海拔蟾蜍的 Hbs 还具有明显的低温强波尔效应和低温敏感性。血液学特征的适应性调整可以增强高海拔中华蟾蜍的血液-O 携带能力。增加的 Hb-O 亲和力可以在缺氧下保护肺上传 O。低温下的强波尔效应可以帮助代谢组织和冷肢体释放 O，而低温敏感性可以最大限度地减少温度波动对 Hb-O 亲和力的影响。
