Ju Y-I, Sone T, Okamoto T, Fukunaga M
Dept. of Nuclear Medicine, Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan.
J Appl Physiol (1985). 2008 Jun;104(6):1594-600. doi: 10.1152/japplphysiol.01004.2007. Epub 2008 Apr 17.
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.
研究了尾部悬吊的幼年生长大鼠股骨的三维小梁结构，并检测了再活动期间跳跃运动的影响。将5周龄雄性Wistar大鼠（n = 35）随机分为五个体重匹配组：尾部悬吊组（SUS；n = 7）；SUS的久坐对照组（S(CON)；n = 7）；尾部悬吊后的自发恢复组（S+R(CON)，n = 7）；尾部悬吊后的跳跃运动组（S+R(JUM)；n = 7）；以及与S+R(CON)和S+R(JUM)年龄匹配的无尾部悬吊和运动的对照组（S(CON)+R(CON)；n = 7）。SUS和S(CON)组的大鼠在尾部悬吊14天后立即处死。跳跃运动方案包括每天10次跳跃，每周5天，跳跃高度为40厘米。测量了股骨的骨密度（BMD）和股骨远端干骺端的三维小梁骨结构。尾部悬吊导致股骨总BMD下降13.6%（P < 0.001），小梁结构明显恶化。自由再活动5周后，股骨BMD、小腿肌肉重量和体重恢复到年龄匹配的对照水平，但小梁仍然更细且连接更少。另一方面，与S+R(CON)组大鼠相比，S+R(JUM)组大鼠的小梁厚度、数量和连接性显著增加（分别为62.8%、31.6%和24.7%；P < 0.05），并且这些小梁结构参数恢复到S(CON)+R(CON)组的水平。这些结果表明，悬吊引起的小梁退化在再活动后仍然存在，但再活动期间的跳跃运动可以恢复幼年生长大鼠股骨小梁结构和骨量的完整性。
