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Alveolar size, number, and surface area: developmentally dependent response to 13% O2
L N Blanco1, D Massaro, G D Massaro
1Lung Biology Laboratory, Georgetown University Medical Center, Washington, DC 20007.
The American Journal of Physiology
|December 1, 1991
Summary
Hypoxia (low oxygen) exposure during pregnancy and early life impairs lung development in rat pups, affecting alveolar formation. However, later exposure can enhance lung surface area and volume.
Area of Science:
- Pulmonary physiology
- Developmental biology
- Environmental medicine
Background:
- Lung development involves the formation and maturation of gas-exchange structures, primarily alveoli.
- Exposure to altered oxygen levels can significantly impact developmental processes.
Purpose of the Study:
- To investigate the effects of chronic hypoxia (13% O2) on lung development in rats during gestation, lactation, and early postnatal life.
- To determine how developmental stage influences the response of lung structures to hypoxic conditions.
Main Methods:
- Stereological methods were used to estimate the volume (v), number (N), and surface area (Sa) of gas-exchange structures (saccules/alveoli) in rat lungs.
- Rats were exposed to 13% O2 or ambient air (control) at different life stages: pre-conception, throughout pregnancy, lactation, and post-weaning.
Main Results:
- Hypoxia during early development (2-14 days) impaired saccule-to-alveoli conversion, leading to reduced alveolarization and smaller alveolar volume.
- Between 14 and 40 days, hypoxic pups showed a reduced increase in alveolar volume but a greater increase in alveolar number compared to controls.
- Post-weaning exposure (23-44 days) to hypoxia resulted in increased lung surface area and volume, with no change in alveolar number.
Conclusions:
- Lung alveolar formation and surface area expansion involve multiple mechanisms that are sensitive to oxygen levels.
- The developmental stage at which hypoxic exposure occurs critically influences the lung's structural response, highlighting a developmentally dependent effect.