Effects of 1 Gray radiation on the biophysical properties of the tibia and femur from hindlimb‐suspended rats

Abstract Long‐term space travel (e.g. travel to Mars) will greatly exceed the recommended lifetime radiation dose of 600 millisieverts (mSv) and have a detrimental effect on skeletal fragility. Our objective was to determine if 1 Gray (GY) radiation impacts the biomechanical properties of the tibia and femur from rats under microgravity. Hindlimb‐suspended male Sprague–Dawley rats were irradiated (IR) with 1 GY (+IR) or used as control (−IR); after 4 weeks they were sacrificed to obtain the femur and tibia. Using the three‐point bending technique, we found radiation had no effect on the flexure force/bending and stiffness of the femur. However, the tibias from the +IR rats demonstrated 37% less flexure force/bending and stiffness than −IR rats. Bone elemental analysis was determined using a scanning electron microscope equipped with energy dispersive spectroscopy; there was no difference in the calcium/phosphorus ratio between +IR and −IR groups. This study provides pilot data which suggest that low dose radiation exposure has a greater impact on the smaller hindlimb bones from hindlimb‐suspended rats.