Ethane-1-hydroxy-1, 1-diphosphonate (EHDP). Effects on growth and modeling of the rat tibia.

One hundred gram male Sprague-Dawley rats were divided into groups which were injected daily for 10 or 30 days with vehicle (control group), 0.2, 0.4, 2.0, or 10.0 mg ethane-1-hydroxy-1,1-diphosphonate (EHDP)/kg/day. The proximal tibial metaphysis and epiphysis were assayed for changes in percentage of hard tissue and bone formation factors. Knowing these, information about hard tissue resorption was deduced. After ten or thirty days treatment with 2.0 or 10.0 mg EHDP/kg/day, there was an increase in percentage of hard tissue. This was due to a decrease in bone formation with a greater decrease in hard tissue resorption. Furthermore, after thirty days treatment with 0.2 and 0.4 mg EHDP/kg/day, there was an increase in percentage of hard tissue, which was due to a decrease in resorption with no change in formation. Ultrastructural studies on osteoclasts from EHDP-treated rats showed a general decrease in their vacuolization and amount of organelles as dosage of EHDP increased. Histologic findings suggest that EHDP is similar to fluoride in the way in which it depresses hard tissue resorption.