pH Effect on Erythropoietin Response to Hypoxia

Six normal volunteers were exposed to a simulated altitude of 4500 meters, and changes in urine and serum erythropoietin levels were related to the changes in acid-base status. During the initial six hours of exposure the volunteers had respiratory alkalosis, which produced a definite increase in red-cell oxygen affinity. These conditions were associated with an increase in urinary and serum erythropoietin. The continued alkalosis and hypocapnia gradually raised red-cell 2,3-diphosphoglycerate concentrations and lowered red-cell oxygen affinity. These changes are thought to lead to the decreased erythropoietin concentration seen after continued exposure. Treatment of the same volunteers with acetazolamide prevented the initial respiratory alkalosis and reduced erythropoietin response. These findings demonstrate that erythropoietin concentrations in urine and serum were influenced by the acid-base status of the volunteers.