Study on oxidation stability and oxygen affinity of hemoglobin during storage.

The factors affecting hemoglobin (Hb) oxidation in its short- and long-term storage were investigated. Porcine Hb with different levels of oxygen saturation was stored at 25 degrees C or 4 degrees C for 40 days. The methemoglobin (metHb) content increased rapidly when Hb was at half saturation with oxygen at 4 degrees C, increased gradually with the increase in Hb oxygenation or deoxygenation, and was almost unchanged when Hb was highly oxygenated or deoxygenated. The Hb oxidation was more intense when stored at 25 degrees C. This indicated that highly oxygenated or deoxygenated Hb can be stored short term at 4 degrees C. The accelerated test showed that metHb content was almost unchanged when Hb was highly deoxygenated and stored at 37 degrees C for 7 days; however, the metHb content rapidly increased when Hb was highly oxygenated and stored at 37 degrees C, which indicated that only highly deoxygenated Hb is suitable for long-term storage. Then, the long-term oxidation stability of highly deoxygenated Hb and polymerized hemoglobin was verified; the metHb content of both did not show significant changes at 4 degrees C for 18 months. Moreover, the results in this work indicated that a temperature increasing from 20 to 40 degrees C clearly increased the partial oxygen pressure (P50), which represents decreased oxygen affinity and is beneficial to deoxygenation. Furthermore, P50 was increased when the pH decreased from 9 to 7. Therefore, we concluded that the appropriate high temperature and neutral condition in vitro are conducive to reducing the oxygen affinity of Hb to achieve efficient deoxygenation, which could promote the development of hemoglobin-based oxygen carriers.