成長期ラットの運動負荷による脛骨骨幹皮質骨への影響

抄録

Six-week-old male Wistar rats, corresponding to early childhood in human, were divided into 6 groups : control group (A), standard diet・1-exercise group (B), standard diet・2-exercise group (C), calcium deficient diet・no-exercise group (D), calcium deficient diet・1-exercise group (E), calcium deficient diet・2-exercise group (F). Running exercise was scheduled as 5 days a week at a speed of 20m/min. The effects of running exercise and calcium intake were investigated on bone formation. I. Body weight Group F showed significantly lower weight than any of groups A, B, C and D (p<0.05). II. Bone density measurement with Softex radiography Standard diet group showed significantly higher density than calcium deficient diet groups (p<0.01). III. Microscopic findings Of those fed with standard diet, group B showed increased Haversian system, Haversian lamillae, interstitial lamillae and osteocytic lacnae compared with grope A. Bone remodeling was activated as demonstrated by cement lines. Grope C showed scattered marrow cavity and irregularity of osteocytic lacunae. Cement line and remordelling layer showed decreased in group C, compared with those in group A. In contrast to standard diet groups, calcium deficiency groups showed decreased width of compact bone and increased resorption. Bone marrow was seen in bone matrix and number of osteocytic lacnae decreased. Group E hardly showed any significant effect of exercise compared with group D. Group F showed less bone matrix formation and thinned cortical bone, compared with groups D and E, with bone marrow cavity and bone resorption increased within matrix. IV. SEM findings Of those fed with standard diet, group B showed expanded bone formation area and more osteocytic lacunae compared with Group A, and densely arranged collagens were seen on lacunar wall. Group C showed increased resorption area compared with groups A and B, and shallow plate-shaped resorptive lacunae were seen here and there. Calcium deficiency groups showed more expanded resorptive area than formative one, compared with standard diet group, and resorptive lacunae of irregular shape were present. No clear demarcation could be identified between bone formation and its surrounding matrix. Of those fed with calcium deficient diet, group E showed almost the same findings as group D, while group F showed expanded resorptive area compared with groups D and E, and boundary of resorptive lacuna was not clear. V. Hematological test As compared with group B and C, group D and E showed lower serum Ca level (p<0.01). Group D showed lower ratio of serum calcium and phosphorus than those fed with standard diet (p<0.01). From the above results, it showed that appropriate physical exercise facilitated in bone formation and accumulation of bone mass, while excessive exercise showed negative effect. Calcium deficiency prohibited the effectiveness of exercise.