[Effect of different doses of alpha-hydroxydimethyl-gamma-aminopropylidene biphosphonate on rat bones]

For 10 days rats were subcutaneously injected with alpha-hydroxydimethyl-gamma-aminopropylidene biphosphonate in the dose range 0.005 to 5 mg/kg/day. As shown morphometrically, the mass of spongy bone increased linearly with the dose. It was found that the drug affected primarily the highly metabolic component of spongy bone. The drug had a systemic osteotrophic effect and modified the number of osteocytes significantly. When the drug was injected for a long time (up to 60 days), the number of osteoclasts decreased and the proportion of cells containing more than one nucleus remained within normal limits. The number of osteoblasts either diminished (in long bones) or remained unchanged (in torso and pelvic bones). It is concluded that the osteotrophic effect of the drug is mediated via its action on bone resorption the rate of which is inhibited; this is responsible for bone mass growth.