[Kinetics of hemoglobin carrying and releasing oxygen]

The purpose of the present study was to examine the kinetic process of hemoglobin (Hb) carrying and releasing oxygen. Under the standard conditions (pH 7.4, Po(2) 20 mmHg, 20 °C) the blood samples of chicken, rabbit, frog and carp were equilibrated in oxygen content analyzer with calibrated gas mixture A (0.5% CO(2) and 99.5% N(2)). Then the blood samples were exposed to gas mixture B (21% O(2), 0.5% CO(2) and 78.5% N(2)). After equilibration, the blood samples were exposed to gas mixture A again. During the whole process, Po(2) of blood samples was detected in real-time. The time spent in blood Po(2) changing from 0 to 21 kPa was recorded carefully. The results indicated that the kinetic curve of Hb carrying oxygen presented a shape of "S". It was similar to the Hb oxygen dissociation curve (Hb ODC). Based on the curve, T(50), a new kinetic parameter, was established. T(50) is the time of 50% O(2) saturation of Hb. It can reflect the efficiency of Hb carrying oxygen. Through comparing of T(50), the efficiency of Hb carrying oxygen among 4 species of animals was: frog < carp < rabbit < chicken. In the phase I of Hb carrying and releasing oxygen kinetic curve, the slope in carp was much larger than that in rabbit; the time [(1 411±6) s] of Hb releasing oxygen in chicken was longer than that in other 3 animals. These differences reflected the variety of efficiency of Hb carrying and releasing oxygen. In addition, the kinetic features of Hb carrying oxygen were likely to become an important index to evaluate the function of Hb carrying oxygen, especially in evaluating the ability of artificial blood substitute. On the basis of the analysis of the kinetic curve of Hb carrying oxygen and Hb ODC, another new important efficacy parameter E(50) was proposed. E(50) reflects the relationship between the time of 50% O(2) saturation of Hb and environmental Po(2). E(50) can be used as a synthetic index to assess the efficiency of Hb carrying oxygen.