| Keywords |
Rat ; Tail suspension ; Forelimb ; Hindlimb ; Bone mineral density (BMD) |
| Abstract |
Mechanical forces play a pivotal role in maintaining bone mass. Tail-suspension has long been employed to induce a pattern of osteopenia in rats and it has been used as a ground-based model for the spaceflight. This study was designed to clarify the change of BMD between the fore- and hind-limb induced by non-weight-bearing, eighteen 7-week-old female spraque-dawley rats completed tail-suspension for 2-week. After a week of stabilization, rats were randomly divided into three groups: before tail-suspension group (n = 6, before), non-suspension control group (n = 6, Con) and tail-suspension group (n = 6, Sus). The rats were fed standard lab chow (CRF-1, Charles River, Japan) and water ad libitum while Con group were pair fed with the appropriate suspension rats for control of caloric intake. At before and after 2-week suspension, rats were sacrificed and femur and humerus were removed for analysis of bone mineral density (BMD) by dual energy X-ray absorptionmetry (DEXA, Lunar DPXL, USA). Serum and twenty four hours urinary calcium (Ca) and phosphate (P) were determined by biochemical markers of bone metabolism. BMD of femur in the Con group were increased in approximately 16.5% as compared with that of the before group (p < .001), but that of the Sus group did not increased, and showed approximately 11.2% lower than that of the Con group (p < .01). However, BMD of humerus in the both group showed no difference between the Con and the Sus group (NS). Similarly, BMC of femur in the Con group were increased in approximately 45.5% as compared with that of the before group (p < .001), but that of the Sus group was small, and showed approximately 14.5% lower than that of the Con group (p < .01). However, BMC of humerus in the both group showed no difference between the Con and the Sus group (NS). The femur weight of the Sus group was decreased approximately in 8% as compared to the Con group (p < .05), but the humerus weight showed no difference between the Con and the Sus group. On the other hand, the serum Ca concentration and twenty four hours urinary Ca excretion between the Con and the Sus group showed similar levels. Twenty four hours urinary P excretion of the Sus group, however, dynamically decreased approximately 50% lower than that of the Con group (p < .05) while serum P concentration was increased (p < .001). These results suggest that the bone loss was occurred mainly a part of non-weight bearing, and that disturbed P homeostasis in this process. |