Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada.
Respir Physiol Neurobiol. 2013 Mar 1;186(1):45-52. doi: 10.1016/j.resp.2012.12.011. Epub 2013 Jan 8.
Animals native to hypoxic environments have adapted by increasing their haemoglobin oxygen affinity, but in-vitro studies of the oxyhaemoglobin dissociation curve (ODC) in humans show no changes in affinity under physiological conditions at altitudes up to 4000m. We conducted the first in-vivo measurement of the ODC; inducing progressive isocapnic hypoxia in lowlanders at sea level, acutely acclimatized lowlanders at 3600m, and native Andeans at that altitude. ODC curves were determined by administering isocapnic steps of increasing hypoxia, and measuring blood oxygen partial pressure and saturation. The ODC data were fitted using the Hill equation and extrapolated to predict the oxygen partial pressure at which haemoglobin was 50% saturated (P50). In contrast to findings from in-vitro studies, we found a pH-related reduction in P50 in subjects at altitude, compared to sea-level subjects. We conclude that a pH-mediated increase in haemoglobin oxygen affinity in-vivo may be part of the acclimatization process in humans at altitude.
原产于低氧环境的动物通过增加血红蛋白的氧亲和力来适应环境，但在海拔高达 4000 米的生理条件下，对人体氧合血红蛋白解离曲线（ODC）的体外研究表明，亲和力没有变化。我们进行了 ODC 的首次体内测量；在海平面的低地居民中诱导进行性等碳酸缺氧，在 3600 米的急性适应低地居民，以及在那个海拔高度的安第斯人。通过给予等碳酸缺氧的递增步骤来确定 ODC 曲线，并测量血氧分压和饱和度。使用 Hill 方程拟合 ODC 数据，并进行外推以预测血红蛋白 50%饱和时的氧分压（P50）。与体外研究的结果相反，我们发现与海平面组相比，海拔组的 P50 与 pH 有关。我们得出结论，体内血红蛋白氧亲和力的 pH 介导增加可能是人类高原适应过程的一部分。
