Jump exercise during remobilization restores integrity of the trabecular architecture after tail suspension in young rats.
Three-dimensional trabecular architecture was investigated in the femora of tail-suspended young growing rats, and the effects of jump exercise during remobilization were examined. Five-week-old male Wistar rats (n = 35) were randomly assigned to five body weight-matched groups: tail-suspended group (SUS; n = 7); sedentary control group for SUS (S(CON); n = 7); spontaneous recovery group after tail suspension (S+R(CON), n = 7); jump exercise group after tail suspension (S+R(JUM); n = 7); and age-matched control group for S+R(CON) and S+R(JUM) without tail suspension and exercise (S(CON)+R(CON); n = 7). Rats in SUS and S(CON) were killed immediately after tail suspension for 14 days. The jump exercise protocol consisted of 10 jumps/day, 5 days/wk, and jump height was 40 cm. Bone mineral density (BMD) of the femur and three-dimensional trabecular bone architecture at the distal femoral metaphysis were measured. Tail suspension induced a 13.6% decrease in total femoral BMD (P < 0.001) and marked deterioration of trabecular architecture. After 5 wk of free remobilization, femoral BMD, calf muscle weight, and body weight returned to age-matched control levels, but trabeculae remained thinner and less connected. On the other hand, S+R(JUM) rats showed significant increases in trabecular thickness, number, and connectivity compared with S+R(CON) rats (62.8, 31.6, and 24.7%, respectively; P < 0.05), and these parameters of trabecular architecture returned to the levels of S(CON)+R(CON). These results indicate that suspension-induced trabecular deterioration persists after remobilization, but jump exercise during remobilization can restore the integrity of trabecular architecture and bone mass in the femur in young growing rats.
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Dept. of Nuclear Medicine, Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan.
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Okamoto
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Fukunaga
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D000818:Animals; D001835:Body Weight; D015519:Bone Density; D005269:Femur / Q000000981:diagnostic imaging / Q000254:growth & development / Q000473:pathology*; D019417:Hindlimb Suspension; D021621:Imaging, Three-Dimensional; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology; D009929:Organ Size; D005082:Physical Exertion; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014057:Tomography, X-Ray Computed