亜鉛がラット下顎頭軟骨の成長発育に及ぼす影響 : 活性型ビタミン D_3 の併用

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Five-week-old male Wistar rats, corresponding to childhood in human beings, were used to investigate the effect of zinc and activated vitamin D_3 (VD_3) administration on bone formation induced by endochondral ossification. The animals were divided into such 4 groups as control, standard diet and VD_3, low zinc diet and VD_3, and high zinc diet and VD_3 groups. 1. Densitometric measurement Differences were statistically significant between control and high zinc diet and VD_3 and between control and standard diet and VD_3 groups (p<0.01). 2. X-ray microanalysis of Ca and P As compared with control group, relative ratio of Ca was higher in standard diet and VD_3 and high zinc diet and VD_3 groups, while lower in low zinc diet and VD_3. In contrast, relative ratio P was lower in standard diet and VD_3 and high zinc diet and VD_3 groups, while higher in low zinc diet and VD_3 group. 3. Histopathologic findings As compared with control group, standard diet and VD_3 group showed expanded calcified matrix enclosing hypertrophic layer, and increased number of chondroclasts resorbing calcified matrix. Increasad osteoblasts and osteoclasts with active bone formation were revealed next to subcartilaginous bone formative layer. While low zinc diet and VD_3 group showed less calcified matrix, decreased number of chondroclasts, and reduced subcartilaginous bone formation. Thin trabeculae were arranged almost perpendicularly. As compared to standard diet and VD_3 group, high zinc diet and VD_3 group showed enlarged chondrocytes evenly distributed in hypertrophic layer, with calcified matrix around. Number of chondroclasts and invasion of calcified matrix around were revealed increased, which was continued with densely arranged bone trabeculae where bone formation was identified active by increased osteoblasts and osteoclasts. 4. SEM findings As compared with control group, standard diet and VD_3 group showed expansive areas of bone resorption and formation in matrix with active new bone formation. While low zinc diet and VD_3 group showed indistinct cartilage lacunae where irregularly scattered calcified vesicles and cord-like distributed collagen fibrils were seen ; bone trabeculae were thinned and irregularly arranged. As Compared with standard and VD_3 group, high zinc diet and VD_3 group showed that lacunae were clearly demarcated by matrix formed by fused calcified vesicles, with more collagen fibrils calcified on bottom of the lacunae. Active bone formation was seen while bone formation and resorption areas mixed. From the above results, VD_3 administration facilitated in bone formation in rat's condylar cartilge, but it was shown that adequate zinc intake would promote the action of VD_3, because the present study had revealed that bone structure was damaged by insufficiency of zinc intake.
九州歯科学会の論文
1998-10-25

亜鉛がラット下顎頭軟骨の成長発育に及ぼす影響 : 活性型ビタミン D_3 の併用

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