The effects of X-ray radiation on mandibular bone of low-calcium diet rats

In an attempt to examine the effects of X-ray on osteoporosis, a single dose of 30 Gy was delivered to the mandible in rats given low-calcium diet. Serum levels of calcium (Ca) and inorganic phosphorus (P) were measured; and changes in bone salt were determined by autoradiography, microradiography, and roentgenography using an electron probe microanalyzer. Body weight was lower in the irradiated group than the non-irradiated group, irrespective of types of diet. The serum Ca levels in the irradiated group given a normal diet were significantly decreased on Days 3, 7, and 14 days after irradiation. When given a low-Ca diet, these levels tended to be lower in the irradiated group than the non-irradiated group on Day 7 or later. The serum levels of inorganic P were significantly lower in the irradiated group given a normal diet than the non-irradiated group on Day 3. Rats given a low-Ca diet had the same levels, irrespective of irradiation. Autoradiography revealed that Ca-45 retention in the whole jaw was slightly greater in the irradiated group than the non-irradiated group On Days 7 and 21. Rats given a low-Ca diet in both irradiated and non-irradiated groups had a greater Ca-45 retention than those given a normal diet. Microradiography revealed that bone formation-like changes, such as flat surface of the periodontal membrane at the intra-alveolar septum, were slightly noticeable in the irradiated group of rats given a normal diet on Day 21. Thinning of the intra-alveolar septum and decrease of the trabecula at the diaphysis were also noticeable in the irradiated group of rats given a low-Ca diet. Variation of X-ray intensity was more marked on Day 7 than on Day 21 in the irradiated group given a normal diet. When given a low-Ca diet, both the irradiated and non-irradiated group had noticeable X-ray intensity variation. (N.K.)