Hypoxia is defined as the reduced availability of oxygen at high altitude (Bouverot, 1985).  This effect is caused by the lower atmospheric pressure at high altitudes, which  inhibits diffusion of oxygen from the air into the lungs.  Consequently, less oxyhemoglobin is produced resulting  in decreased transport of oxygen to  the tissues (Schmidt-Nielsen, 1997).  Animals may adapt to decreased oxygen availability by increasing the effectiveness of oxygen uptake, thus shifting the oxygen dissociation curve to the left (Schmidt-Nielsen, 1997; Chappell, 1985).  Primarily, increasing oxygen uptake in the lungs is accomplished by decreasing the concentration of the organic phosphate DPG (Snyder, 1982).  Hemoglobin, in the absence of DPG, has a high affinity  for oxygen and consequently will not easily release oxygen to the tissues.  Animals may also adapt to high altitude by maintaining a low oxygen affinity in the hemoglobin (Snyder, 1981).  This mechanism, accomplished by increasing DPG 

A generic oxygen dissociation curve graph demonstrating the effects of DPG.  Increased concentrations of DPG in the hemoglobin decreases the affinity for oxygen (pink), while decreased concentrations of DPG increase the affinity between hemoglobin and oxygen (blue).

to hemoglobin ratios, facilitates delivery of oxygen and  shifts the oxygen dissociation curve to the right.  However, decreasing the affinity of oxygen for hemoglobin inhibits the diffusion of oxygen to the erythrocytes in the lungs. 

Main Page     Introduction     The Oxygen Dissociation Curve     Llama       Deer Mice    Conclusion            

   Acknowledgements     Literature Cited     

This web site was created as a class assignment for Animal Physiology.  Please direct correspondence to jodickens@davidson.edu.

Last Updated November 28, 1999

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