Skeletal response of rats exposed to reduced barometric pressure

¹ Department of Biophysics, The Pennsylvania State University, University Park, Pennsylvania

The response of the rat skeleton to hypoxia (380 mm Hg) has been investigated. The femur images in calibrated radiographs taken at 2-week intervals were analyzed photodensitometrically. Femurs were also excised from other rats to obtain density and volume measurements by displacement methods. Hematocrit values and body weights were recorded. Differences between femur densities and between femur dry weights (hypoxic group 13 and 20% less, respectively) developed during the first 31 days. Differences between femur volumes, between body weights, and between hematocrit values (hypoxic group 8% less, 16% less, and 60% more, respectively) developed during the first 15 days. However, the difference between marrow cavity volumes (hypoxic group 22% more) developed between days 15 and 31. The interpretation is that during the first 15 days when marrow cavity volumes did not differ, the large hematocrit value was caused by increased hemopoietic activity of marrow present at the onset of hypoxia. Subsequently, marrow cavities become 22% larger than normal, facilitating production of blood at a more nearly normal activity.

Key Words: hypoxia • altitude (altitude physiology) • skeleton (bone, bones) • bone density • atmospheric pressure

Submitted on August 28, 1964

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