Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
J Fish Biol. 2014 Mar;84(3):827-43. doi: 10.1111/jfb.12186. Epub 2013 Jul 24.
This study examined mechanisms underlying cardio-respiratory acclimation to moderate sustained hypoxia (6.0 kPa for 7 days at 22° C) in the bowfin Amia calva, a facultative air-breathing fish. This level of hypoxia is slightly below the critical oxygen tension (pcrit ) of A. calva denied access to air (mean ± s.e. = 9.3 ± 1.0 kPa). Before exposure to sustained hypoxia, A. calva with access to air increased air-breathing frequency on exposure to acute progressive hypoxia while A. calva without access to air increased gill-breathing frequency. Exposure to sustained hypoxia increased the gill ventilation response to acute progressive hypoxia in A. calva without access to air, regardless of whether they had access to air or not during the sustained hypoxia. Additionally, there was a decrease in Hb-O2 binding affinity in these fish. This suggests that, in A. calva, acclimation to hypoxia elicits changes that increase oxygen delivery to the gas exchange surface for oxygen uptake and reduce haemoglobin affinity to enhance oxygen delivery to the tissues.
本研究探讨了美洲肺鱼（Amia calva）在 22°C 下中等持续低氧（6.0 kPa，持续 7 天）条件下心肺适应的机制，这种低氧水平略低于禁止呼吸空气的美洲肺鱼的临界氧张力（pcrit，平均值±标准误=9.3±1.0 kPa）。在暴露于持续低氧之前，有空气呼吸机会的美洲肺鱼在急性渐进性低氧暴露时增加空气呼吸频率，而没有空气呼吸机会的美洲肺鱼则增加鳃呼吸频率。暴露于持续低氧会增加没有空气呼吸机会的美洲肺鱼对急性渐进性低氧的鳃通气反应，而不论它们在持续低氧期间是否有空气呼吸机会。此外，这些鱼的血红蛋白与氧的结合亲和力下降。这表明，在美洲肺鱼中，对低氧的适应会引起一些变化，这些变化增加了氧气输送到气体交换表面以进行氧气摄取，并降低血红蛋白对组织的亲和力以增强氧气输送。
