The in-vivo oxyhaemoglobin dissociation curve at sea level and high altitude. 2013

Dahlia Y Balaban, and James Duffin, and David Preiss, and Alexandra Mardimae, and Alex Vesely, and Marat Slessarev, and G R Zubieta-Calleja, and Ernest R Greene, and David B Macleod, and Joseph A Fisher
Institute of Medical Science, University of Toronto, Toronto, ON M5S 1A8, Canada.

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.

UI MeSH Term Description Entries
D008297 Male Males
D009792 Oceans and Seas A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic). Seas,Oceans,Seas and Oceans
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D010108 Oxyhemoglobins A compound formed by the combination of hemoglobin and oxygen. It is a complex in which the oxygen is bound directly to the iron without causing a change from the ferrous to the ferric state. Oxycobalt Hemoglobin,Oxycobalthemoglobin,Oxyhemoglobin,Hemoglobin, Oxycobalt
D005260 Female Females
D006454 Hemoglobins The oxygen-carrying proteins of ERYTHROCYTES. They are found in all vertebrates and some invertebrates. The number of globin subunits in the hemoglobin quaternary structure differs between species. Structures range from monomeric to a variety of multimeric arrangements. Eryhem,Ferrous Hemoglobin,Hemoglobin,Hemoglobin, Ferrous
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000064 Acclimatization Adaptation to a new environment or to a change in the old. Acclimation
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults
D000531 Altitude A vertical distance measured from a known level on the surface of a planet or other celestial body. Altitudes

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