Effect of chronic centrifugation on bone density of the rat

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Abstract
Alterations in density of the femur of female Sprague-Dawley rats exposed to chronic centrifugation of 2.76 G for 810 days were studied. The density was measured by photon absorptiometry, using a 125I Profile Scanner. The photon absorption measurements were taken: (1) on bone sections from the midshaft of the femur in the anterior, posterior, medial and lateral cortex with the beam path parallel to the shaft axis, and (2) on the femur near the midshaft with the beam path perpendicular to the shaft axis. The latter were correlated with the cross-sectional area in the midshaft. Compared with femora of age-matched rats (age controls) and of rats having body masses comparable to the centrifuged group (weight controls), kept under earth gravity, the chronically centrifuged animals showed on average no significant differences in photon absorption (density) in the four positions in midshaft. The absorption measurements perpendicular to the shaft axis in all groups differe significantly on average. In the relationship to the cross-sectional area there are significant differences between the centrifuged group and the control groups. When cross-sections of equal size are compared, the density of the rat femora is clearly higher in the centrifuged animals than in the control groups. In contrast, the age and weight controls do not differ significantly in density. The results suggest that the increased stress in the rat femora due to centrifugation is reflected in an increased bone density.