Mechanical Properties and Bone Densities for Hypertensive Rat

Abstract

The mechanical properties as well as bone densities of tibia and femur were evaluated for the spontaneously hypertensive rats (SHR) and the salt-sensitive hypertensive rats (Dahl S). Dynamic stiffness and loss tangent(tanδ) were measured with a viscoelastic spectrometer. The three-point bending tests were performed with an Instron-type universal testing machine. Bone mineral content was measured by the peripheral quantitative computed tomography (pQCT) at the middle site of the tibia and the femur. Three kinds of bone samples were used: Group1 samples were taken from 36-week-old SHR. Group2 were taken from the salt-sensitive hypertensive rats fed with high saline meals from 12 to 34 weeks old. Group3 were taken from saltsensitive hypertensive rats fed with high saline meals from 12 to 20 weeks old. The dynamic stiffness and tanδ of the tibia and the femur for SHR decreased significantly compared with Wistar Kyoto Rats (control). For the salt-sensitive rats(Group2) the dynamic stiffness and tanδ of the tibia and the femur also decreased significantly compared with the control. There exists a clear trend in dynamic stiffness and tanδ for Group3. The cortical densities of the bones for Group1 and 2 were significantly different from those of the control. Spontaneously hypertensive rats exhibited higher cortical density than the control and the salt-sensitive rats were lower in density than the control.