Effect of Vitamin D Metabolites on Bone Metabolism in a Rat Model of Postmenopausal Osteoporosis

Abstract

In normal circumstances, two components of bone remodeling, i.e, bone formation and bone resorption, are tightly coupled, so that total bone mass can be maintained. In osteoporosis, these two processes of bone remodeling are uncoupled and the rate of bone resorption exceeds that of bone formation. Although the pathogenesis of osteoporosis is not fully understood, multiple factors have been shown to participate in the development of the disease. These include reduction in sex steroid hormone and calcitonin levels in postmenopausal women (i), a decrease in the renal synthesis as well as the serum levels of 1,25-dihydroxyvitamin D [l,25(OH)2D] (2, 3) and a resultant reduction in intestinal calcium (Ca) absorption (3, 4). As a consequence, there is a negative mineral balance, both at the level of bone and of total body. Therefore, the ideal treatment of osteoporosis would not only be to reduce bone resorption, but also to increase bone formation and to fhaintain positive mineral balance. In an effort to achieve this therapeutic goal, a rat model of postmenopausal osteoporosis was introduced and the effects of various hormones on bone mineral metabolism were examined. © 1985, Center for Academic Publications Japan. All rights reserved.