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Low P50 in deer mice native to high altitude
Journal of Applied Physiology (Bethesda, Md. : 1985)
|January 1, 1985
Summary
High-altitude animals, like the deer mouse, do not necessarily have lower P50 (oxygen partial pressure at 50% hemoglobin saturation) despite lower CO2 levels. Their P50 is influenced by various factors, supporting theories of adaptation to hypoxia.
Area of Science:
- Physiology
- Altitude Biology
- Comparative Physiology
Background:
- High-altitude animals are often presumed to have lower P50 (oxygen partial pressure at 50% hemoglobin saturation) for improved oxygen uptake.
- This widely held belief lacks robust empirical documentation across different altitudes.
Purpose of the Study:
- To investigate the relationship between native altitude and hemoglobin-oxygen binding affinity (P50) in Peromyscus maniculatus.
- To determine P50, PCO2, Bohr effect, and buffer slope in deer mice acclimated to different altitudes.
Main Methods:
- Utilized the mixing technique to measure P50, PCO2, and buffer slope.
- Acclimated Peromyscus maniculatus to two distinct altitudes: 340 m and 3,800 m.
- Analyzed P50 at a standard pH of 7.4 (P50(7.4)).
Main Results:
- PCO2(7.4) and buffer slope were significantly lower at high altitude (3,800 m).
- The change in P50(7.4) between acclimation altitudes was minimal (0.8% increase at 3,800 m).
- A significant negative correlation was observed between P50(7.4) and native altitude.
Conclusions:
- Altitude-induced changes in P50 are complex, involving counterbalancing factors like 2,3-diphospho-D-glycerate concentration.
- The findings support theoretical predictions that a lower P50 is advantageous under hypoxic stress.
- Observed P50 differences may be underestimated due to in vivo pH adjustments at high altitude.