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Title: High blood oxygen affinity in the air-breathing swamp eel Monopterus albus
Authors: Damsgaard, Christian
Đỗ, Thị Thanh Hương
Fago, Angela
Weber, Roy E.
Buchanan, Rasmus
Kocagoz, Yigit
Helbo, Signe
Findorf, Inge
Bayley, Mark
Wang, Tobias
Keywords: Air-breathing
Issue Date: 2014
Series/Report no.: Comparative Biochemistry and Physiology;178 .- p.102–108
Abstract: The Asian swamp eel (Monopterus albus, Zuiew 1793) is a facultative air-breathing fish with reduced gills. Previous studies have shown that gas exchange seems to occur across the epithelium of the buccopharyngeal cavity, the esophagus and the integument, resulting in substantial diffusion limitations that must be compensat- ed by adaptations in others steps of the O₂ transport system to secure adequate O₂ delivery to the respiring tissues. We therefore investigated O₂ binding properties of whole blood, stripped hemoglobin (Hb), two major isoHb components and the myoglobin (Mb) from M. albus. Whole blood was sampled using indwelling catheters for blood gas analysis and determination of O₂ equilibrium curves. Hb was purified to assess the effects of endog- enous allosteric effectors, and Mb was isolated from heart and skeletal muscle to determine its O₂ binding prop- erties. The blood of M. albus has a high O₂ carrying capacity [hematocrit (Hct) of 42.4 ± 4.5%] and binds O₂ with an unusually high affinity (P₅₀ = 2.8 ± 0.4 mmHg at 27 °C and pH 7.7), correlating with insensitivity of the Hb to the anionic allosteric effectors that normally decrease Hb-O₂ affinity. In addition, Mb is present at high concen- trations in both heart and muscle (5.16 ± 0.99 and 1.08 ± 0.19 mg ∙ g wet tissue-1, respectively). We suggest that the high Hct and high blood O₂ affinity serve to overcome the low diffusion capacity in the relatively ineffi- cient respiratory surfaces, while high Hct and Mb concentration aid in increasing the O₂ flux from the blood to the muscles.
URI: http://localhost:8080//jspui/handle/123456789/5113
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