Induction of osteopenia in confined rats.

We have developed a simple model of osteopenia in rats which is induced by confinement without requiring surgical operation. Each rat was maintained for 8 weeks in a compartment of a commercially-available wire netting cage subdivided into 10 areas (compartment size, 9 x 16 x 14 cm) to restrict exercise. The femora isolated from the confined rats showed significant decreases in mineral (calcium and phosphorus) content, compared with the level in normal rats, 2 weeks after the start of their confinement. Confined rats showed significantly lower values for the physical properties of bones such as breaking energy and breaking force and also density composed with normal rats 4 weeks after the start of confinement. KCA-098 (1 mg/kg), a new benzofuroquinoline derivative that inhibits bone resorption and at the same time stimulates bone mineralization in organ culture, protected against these decreases when given orally for 8 weeks. All these results show that confinement of rats offers a simple and useful animal model of osteopenia.