Hb Linköping (beta 36 Pro----Thr): a new high oxygen affinity hemoglobin variant found in two families of Finnish origin

Influence of High Hemoglobin-Oxygen Affinity on Humans During Hypoxia

Humans elicit a robust series of physiological responses to maintain adequate oxygen delivery during hypoxia, including a transient reduction in hemoglobin-oxygen (Hb-O₂) affinity. However, high Hb-O₂ affinity has been identified as a beneficial adaptation in several species that have been exposed to high altitude for generations. The observed differences in Hb-O₂ affinity between humans and species adapted to high altitude pose a central question: is higher or lower Hb-O₂ affinity in humans more advantageous when O₂ availability is limited? Humans with genetic mutations in hemoglobin structure resulting in high Hb-O₂ affinity have shown attenuated cardiorespiratory adjustments during hypoxia both at rest and during exercise, providing unique insight into this central question. Therefore, the purpose of this review is to examine the influence of high Hb-O₂ affinity during hypoxia through comparison of cardiovascular and respiratory adjustments elicited by humans with high Hb-O₂ affinity compared to those with normal Hb-O₂ affinity.

An improved biotonometric method for determination of haemoglobin oxygen equilibrium curves

A new biotonometric method for the determination of haemoglobin oxygen equilibrium curves is described. The procedure is based on the mixing of an oxygen-consuming organism, the yeast cell (Saccharomyces cerevisiae), with an oxidized blood/plasma mixture. The yeast cell consumes oxygen at a uniform rate, thus reducing the partial pressure of oxygen in the mixture. This in turn induces the dissociation of oxygen in a characteristic manner. The study of the whole blood samples from 26 healthy volunteer subjects gave the following results: p50 = 3.63 kPa +/- 0.23 kPa (mean +/- 1 S.D.); Hill slope n = 2.44 +/- 0.16; and CO2 Bohr factor = -0.47 +/- 0.11. For the within-run imprecision the coefficients of variation for the different parameters were: p50 C.V. = 4.4%; Hill slope n C.V. = 4.7%; and CO2 Bohr factor C.V. = 19%. The determination can be carried out with simple equipment: a blood gas analyzer with a coupled recorder.

Effect of hemodilution on maximal oxygen consumption, blood lactate response to exercise and cerebral blood flow in subjects with a high-affinity hemoglobin

10 subjects with Hb Linköping (beta 36 Pro greater than Thr), a high-affinity hemoglobin variant, with a P50 of 2.2 kPa (16.5 mm Hg) were investigated before and 3-4 days after normovolemic hemodilution. Blood hemoglobin concentration decreased from 176 +/- 13 (SD) to 146 +/- 15 g l-1 and the red cell volume from 2.77 +/- 0.83 to 2.23 +/- 0.67 l. Maximal oxygen consumption decreased slightly by 2.7 +/- 3.8 ml min-1 kg-1 and maximal exercise power by 11 +/- 23 W; these changes were, however, not statistically significant. Maximal heart rate was unchanged (-1.1 +/- 6.4 beats min-1) while submaximal heart rate was consistently increased on comparable loads after hemodilution compared to before. The exercise ECG was normal both before and after hemodilution. Capillary lactate levels at exercise were always higher after hemodilution than before. Cerebral blood flow was normal both before and after hemodilution in all subjects but one who had a high flow. The grey matter blood flow increased slightly but significantly by 8.6 +/- 10.3 ml min-1 100 g-1 from before to after hemodilution. The results indicate that subjects with Hb Linköping have only limited benefit from their increased blood hemoglobin concentration.