Effects of ethane-1-hydroxy-1,1-diphosphonate (EHDP) upon the kinetics of bone resorption and bone formation at the whole bone level in prelabelled chicks.

Chicks chronically prelabelled with 45Ca, 3H-tetracycline, and 3H-proline were used to measure the weekly effect of EHDP (5 mg P/kg for 28 days) on bone turnover at the whole bone level in vivo. Direct measurements were made of cortical bone resorption (loss of 3H-tetracycline and 3H-collagen from whole femur, blood-bone ratio of 45Ca), skeletal collagen formation and bone mineralization (collagen and calcium mass per whole femur, respectively). Chicks were sacrificed after 5, 14, 21 and 28 days of EHDP administration. By five days of treatment, EHDP caused a greater inhibition of bone mineralization (86%) than bone resorption (30-39%) without affecting skeletal collagen mass. The blood-bone ratio of 45Ca decreased 34%, which was similar in degree to the inhibition of 3H-tetracycline loss (30%) and 3H-collagen loss (39%). Almost complete inhibition of bone resorption and bone mineralization occurred by 14 days of treatment without effects on skeletal collagen mass. No additional effect was seen at 21 and 28 days of EHDP treatment. In chicks, EHDP inhibits almost completely bone mineralization (bone formation) and cortical bone resorption without affecting skeletal collagen mass.