Jensen F B, Wang T, Jones D R, Brahm J
Institute of Biology, Odense University, Denmark.
Am J Physiol. 1998 Mar;274(3):R661-71. doi: 10.1152/ajpregu.1998.274.3.R661.
Deoxygenation of alligator red blood cells (RBCs) caused binding of two HCO3- equivalents per hemoglobin (Hb) tetramer at physiological pH. At lowered pH, some HCO3- binding also occurred to oxygenated Hb. The erythrocytic total CO2 content was large, and Hb-bound HCO3-, free HCO3-, and carbamate contributed about equally in deoxygenated cells. The nonbicarbonate buffer values of RBCs and Hb were high, and the Hb showed a significant fixed acid Haldane effect. Binding of HCO3- on deoxygenation occurred without a change in RBC intracellular pH, revealing equivalence between oxylabile HCO3- and H+ binding. Erythrocyte volume, plasma pH, and plasma HCO3- concentration also varied little with the degree of oxygenation. Diffusional water permeability was higher in oxygenated than deoxygenated RBCs. The RBCs have rapid band 3-mediated Cl- and HCO3- transport, which was not affected by degree of oxygenation, but net fluxes of Cl- and HCO3- via the anion exchanger are small during blood circulation at rest. Most of the CO2 taken up into the blood as it flows through tissue capillaries is carried within the erythrocytes as Hb-bound HCO3- until CO2 is excreted when blood flows through pulmonary capillaries.
短吻鳄红细胞（RBCs）的脱氧作用导致在生理pH值下每个血红蛋白（Hb）四聚体结合两个HCO₃⁻等价物。在较低pH值时，一些HCO₃⁻也会与氧合Hb结合。红细胞的总二氧化碳含量很高，在脱氧细胞中，与Hb结合的HCO₃⁻、游离HCO₃⁻和氨基甲酸盐的贡献大致相等。红细胞和Hb的非碳酸氢盐缓冲值很高，并且Hb表现出显著的固定酸哈代效应。脱氧时HCO₃⁻的结合发生在红细胞细胞内pH值无变化的情况下，揭示了易氧化的HCO₃⁻与H⁺结合之间的等效性。红细胞体积、血浆pH值和血浆HCO₃⁻浓度也随氧合程度变化很小。氧合红细胞的扩散水渗透性高于脱氧红细胞。红细胞具有快速的带3介导的Cl⁻和HCO₃⁻转运，这不受氧合程度的影响，但在静息血液循环期间，通过阴离子交换器的Cl⁻和HCO₃⁻净通量很小。当血液流经组织毛细血管时，进入血液的大部分CO₂以与Hb结合的HCO₃⁻形式携带在红细胞内，直到血液流经肺毛细血管时CO₂被排出。
