[Reaction of osseous tissue and the osteoclast population in rats to biphosphonates and vitamin D3 under conditions of hypokinesia].

Oral administration of hydroxy-dimethyl aminopropylene biphosphonate (DMAP) at a dose of 0.5 mg/kg increased the volume density (mass) of trabecular bone in the tibial metaphysis of untreated rats and helped to maintain it at the normal level in hypokinetic rats. Oral administration of hydroxy-ethylidene biphosphonate (OEDP) at a dose of 20 mg/kg and vitamin 24,25(OH)2D3 at a dose of 1,25 micrograms did not induce any quantitative changes in bones of untreated or immobilized rats.

[Dynamics of immobilization-induced osteoporosis in rats].

Wistar male rats weighing 250-270 g were exposed to hypokinesia for 7, 15, 35 or 60 days. Spongy bone of the metaphysis of long bones, vertebral body, breast bone and iliac bone were examined histomorphometrically. It was found that during hypokinesia osteoporosis developed in two stages: Stage 1 (from hypokinesia day 1 to day 15) was characterized by a drastic bone mass loss due to stress-effects (steroid osteopenia) and Stage 2 (from hypokinesia day 15 to the end) was characterized by adaptive changes which included steady-state development and transition to a lower functional level (immobilization osteoporosis).