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¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1996 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1995 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Human osteoporosis is multifactorial in its etiology, and can result from such conditions as senility, post-menopause and immobilization, as well as changes in endoclinological hormones at general and growth factors and cytokines at local sites. We investigated the mRNA levels of proteins related in bone metabolism.
Experimental osteoporosis was induced by a combination of ovariectomy and immobilization in female Wistar rats. Bilateral sciatic neurectomy was performed in order to immobilize the hind limbs. Rats were orally given 1,25 (OH) 2D3 or a new synthetic vitamin D3 analogue, 2- (3-hydroxypropoxy) -1,25-dihydroxyvitamin D3 [ED-71] twice a week and sacrificed at 1,2,4 and 8 weeks. Bone mineral content was preserved in the ED-71 0.2mug/kg treated group. Serum osteocalcin levels increased in the 1,25 (OH) 2D3 0.2mug/kg and ED-71 0.2mug/kg treated groups at 4 and 8 weeks. Osteocalcin mRNA levels in the bones of the hind limbs which was determined by Northern blot hybridization and increased consistently in the ED-71 0.2mug/kg treated group. These findings suggest that ED-71 may prevent the osteoporotic decrease of bone mass not only by normalizing bone resorption but also by stimulating osteoblasts.
In the in vitro experiment using rat osteosarcoma cells (ROS 17/2.8), osteocalcin mRNA levels increased in a dose-dependent manner when either 1,25 (OH) 2D3 or ED-71 was added to the medium. Osteocalcin mRNA levels of the cells increased when they were exposed to 26,27-F6-1,25 (OH) 2D3 [F6-D3], (an analogue of 1,25 (OH) 2D3). Alkaline-phosphatase mRNA and osteopontin mRNA in the cells also increased when either 1,25 (OH) 2D3 or F6-D3 was added to the medium. In summary, 1,25 (OH) 2D3 and two analogues directly stimulated osteocalcin, alkaline-phosphatase and osteopontin mRNA expression.