Blood: bone disequilibrium. V. Effects of a diphosphonate (EHDP) on phosphate fluxes in rat calvaria.

Calvaria taken from rats (normal or thyroparathyroidectomized) given a diphosphonate (EHDP 10 mg/kg daily for 7 days) were placed in special Ussing chambers for the measurement of phosphate fluxes to and from bone. When compared with appropriate controls, the experimental calvaria showed a marked decrease in influx, K, a significant increase in the projected equilibrium concentration, E/K, where E is the efflux and a significant increase in the calcium concentration in the medium. It is concluded that this large increase in passive "solubility" is caused by the diphosphonate's ability to stabilize the small amount of regulator phase (brushite or brushite-apatite mixture) present in bone.