Which adaptation occurs in response to prolonged low PO2 at high altitudes?

• A. Increased production of hemoglobin
• B. Decreased production of EPO
• C. Increased production of 2,3 DPG
• D. Decreased respiratory rate

Answer: (C)

At high altitudes, the partial pressure of oxygen (PO2) is lower than at sea level, which can lead to hypoxia. The body makes several adaptations to cope with this reduced oxygen availability, one of which includes the increased production of 2,3-diphosphoglycerate (2,3-DPG) in red blood cells.

The rise in 2,3-DPG concentration allows hemoglobin to release oxygen more readily to the tissues. This is crucial at high altitudes where the oxygen supply is limited. By facilitating the release of oxygen, this adaptation enhances tissue oxygenation despite lower ambient oxygen levels. Increased levels of 2,3-DPG effectively shift the oxygen-hemoglobin dissociation curve to the right, which means that for a given partial pressure of oxygen, hemoglobin will release more oxygen to the tissues, thus helping to counteract the effects of low PO2.

Other adaptations can include the increased production of hemoglobin over time as the body tries to improve its oxygen-carrying capacity; however, this response is generally seen more as a longer-term adaptation rather than an immediate response to low PO2. The body also increases production of erythropoietin (EPO) to stimulate red blood