Measurement of Serum [³H]Tetracycline Kinetics and Indices of Kidney Function Facilitate Study of the Activity and Toxic Effects of Bisphosphonates in Bone Resorption

The [³H]tetracycline ([³H]TC) model is based on the observation that TC is released from the bones of rats prelabeled with [³H]TC via first-order kinetics, a factor directly reflecting the kinetics of bone resorption. In the present paper we applied the [³H]TC elimination model to rats treated with antiresorptive drugs. The validity of this model was evaluated by examining the effect of the bisphosphonate, 3-amino-1-hydroxypropylidene-1,1-bisphosphonate (ABP), and a novel bisphosphonate, dihydrogen disodium adipoylbisphosphonate (AdBP), on serum TC levels and the elimination rate constant. ABP and AdBP significantly inhibited the TC elimination rate. However, ABP treatment caused impairment of bone mineralization, renal dysfunction, and inhibition of somatic growth. It is concluded that antiresorptive effects of bisphosphonates could be evaluated by the [³H]TC model, but this model is limited to animals with normal kidney function. The experimental conditions provide a technically simple method which is sensitive enough to examine antiresorptive properties in a healthy animal and to detect adverse effects on the kidney. The activity of the novel bisacylphosphonate, AdBP, and lack of its adverse effects indicate the potential of this drug for clinical applications.