実験的骨粗鬆症に対する活性型ビタミン D_3 の影響に関する X 線的, 光顕的ならびに電顕的研究 : とくに成長期下顎頭の変化

抄録

Three-week-old male rats of Wistar strain were given a calcium-deficient diet and experimental osteoporosis was induced in them. They then were given 1α-OH-D_3 (0.05μg/kg, 3 times/week and 0.1μg/kg, 3 times/week) and its effect on the mandibular condyle and proximal epiphysis of the tibia was investigated radiologically, histopathologically and electronmicroscopically. The results were as follows : I. Radiological findings 1. In the mandibular condyle and proximal metaphysis of tibia, dense osseous layers were more distinct and trabeculae were running more compactly and their widths were narrower in the 0.05D_3 and 0.1D_3 groups than in the calcium-deficient diet group. 2. The tibia epiphysis was formed better in the 0.1D_3 group than in the calciumdeficient diet group or in the 0.05D_3 group. Dense osseous layers were seen in part and trabeculae were increased but were running with their widths narrower. II. Histopathological findings 1. Contact microradiogram findings In the mandibular condyle, tibia epiphysis and tibia metaphysis, the granular trabeculae of primary spongiosa were greater in number and the trabeculae of secondary spongiosa were running with their widths narrower in the 0.05D_3 and 0.1D_3 groups than in the calcium-deficient diet group. 2. General tissue findings i. The cartilage layer in the mandibular condyle and in the tibia epiphysis was thinner due to decrease in proliferative chondrocytes and hypertrophic chondrocytes in the 0.05D_3 and 0.1D_3 groups than in the calcium-deficient diet group. Many findings of erosion of calcified matrix by chondroclasts were seen and subchondrocyte bone formation was increased. Trabeculae however were thinner due to the appearance of osteoclasts. ii. The cartilage layer in the tibia metaphysis was thinner due to decrease in hypertrophic chondrocytes in the 0.05D_3 and 0.1D_3 groups than in the calcium-deficient diet group. Findings of erosion of calcified matrix by chondroclasts were increased and intrachondrocyte bone formation was also increased. Trabeculae however were thinner due to the appearance of osteoclasts. III. Electron microscope findings 1. Scanning electron microscope findings In the three groups, longitudinal matrix in cartilage lacunae of the mandibular condyle were incomplete in many places and collagenous fibrils were not calcified in places. The walls of cartilage lacunae in the areas of subchondrocyte bone formation were composed of incomplete longitudinal matrix. In the base of bone lacunae, large and small openings of bone canalicules were seen clearly. In the calcium-deficient diet group, the areas of subchondrocyte bone formation showed irregular and fewer trabeculae. 2. Transmission electron microscope findings No ultramicrostructual differences in osteoclasts were found in the three groups. In each group, ruffled borders were developed and bone resorption was active. Osteoblasts showed more developed cristae of mitochondria and more cytoplasmic projections in the 0.05D_3 and 0.1D_3 groups than in the calcium-deficient diet group. Collagenous fibrils were seen around the osteoblasts and active bone formation was seen. On the basis of the foregoing findings, dependency on the amount of administration of 1α-OH-D_3 to infirm bone tissue was seen in the mandibular condyle, tibia epiphysis and tibia metaphysis. Growth of cartilage cells was observed and bone formation was the highest in the mandibular condyle with tibia epiphysis and tibia metaphysis following.